Attempt French for the firm (6)
I believe the answer is:
stable
'firm' is the definition.
(similar in meaning)
'attempt french for the' is the wordplay.
'attempt' becomes 'stab' (to have a stab is to attempt something).
'french for the' becomes 'le' ('the' in French).
'stab'+'le'='STABLE'
(Other definitions for stable that I've seen before include "Animal accommodation is steady" , "Constant - place for horses" , "Equine housing" , "farm building" , "far from bats?" .)