Figure fit to be defensible (7)
I believe the answer is:
tenable
'defensible' is the definition.
(thesaurus)
'figure fit' is the wordplay.
'figure' becomes 'ten' (I've seen this in other clues**).
'fit' becomes 'able' ('able' can be similar in meaning to 'fit').
'ten'+'able'='TENABLE'
'to be' acts as a link.
(Other definitions for tenable that I've seen before include "Believable" , "Able to be held" , "Viable" , "fairly arguable" , "okay as regards defence" .)