Extremely clever to revise trust (6)
I believe the answer is:
credit
'trust' is the definition.
(crediting is a kind of trusting)
'extremely clever to revise' is the wordplay.
'extremely' suggests removing the centre.
'to revise' becomes 'edit' (I've seen this before).
'clever' with its middle taken out is 'cr'.
'cr'+'edit'='CREDIT'
(Other definitions for credit that I've seen before include "'Give ...... where ...... is due'" , "Time given to pay for goods" , "Believe; acknowledgement" , "Tick - distinction" , "Time to pay, or due recognition" .)