Full fare is halved - permitted during exercises (7)
I believe the answer is:
replete
'full' is the definition.
('replete' can be a synonym of 'full')
'fare is halved permitted during exercises' is the wordplay.
'is halved' suggests halving the letters.
'permitted' becomes 'let' (I've seen this before).
'during' is an insertion indicator.
'exercises' becomes 'pe'.
'fare' cut in half is 're'.
'let' put inside 'pe' is 'plete'.
're'+'plete'='REPLETE'
(Other definitions for replete that I've seen before include "Filled to satiety" , "Well-supplied" , "Well-fed" , "Full, sated" , "Fully satisfied" .)