Arabinofuranosidase plays an essential role in the process of hydrolysis of arabinoxylan (AX). Thermostable, versatile, and efficient arabinofuranosidase is thus of great interest for the biorefinery industry. A GH51 arabinofuranosidase, Abf51, from Hungateiclostridium clariflavum DSM 19732 was heterogeneously expressed in Escherichia coli. Abf51 was found to have an optimal pH and temperature of 6.5 and 60 °C, respectively, with very high thermostability. At the optimal working temperature (60 °C), Abf51 retained over 90% activity after a 2-day incubation and over 60% activity after a 6-day incubation. Abf51 could effectively remove the arabinofuranosyls from three kinds of AX oligosaccharides [2-α-L-arabinofuranosyl-xylotriose (AXX), 3-α-L-arabinofuranosyl-xylobiose (AX), and 23-di-α-L-arabinofuranosyl-xylotriose (AXX)], which characterized as either single substitution or double substitution by arabinofuranosyls on terminal xylopyranosyl units. The maximal catalytic efficiency (K/K) was observed using p-nitrophenyl-α-L-arabinofuranoside (pNPAF) as a substrate (205.0 s mM), followed by using AX (22.8 s mM), AXX (6.9 s mM), and AXX (0.5 s mM) as substrates. Moreover, the presence of Abf51 significantly stimulated the saccharification level of AX (18.5 g L) up to six times along with a β-xylanase as well as a β-xylosidase. Interestingly, in our survey of top thermostable arabinofuranosidases, most members were found from GH51, probably due to their owning of (β/α)-barrel architectures. Our results suggested the great importance of GH51s as candidates for thermostable, versatile, and efficient arabinofuranosidases toward industry application.