Resent IT spoiling hobby (8)
I believe the answer is:
interest
'hobby' is the definition.
(I've seen this before)
'resent it spoiling' is the wordplay.
'spoiling' indicates anagramming the letters.
'resent'+'it'='resentit'
'resentit' with letters rearranged gives 'INTEREST'.
(Other definitions for interest that I've seen before include "Payment on deposit account" , "Concern - money accruing" , "Deposit account gain" , "Money paid on a loan" , "Sum paid on a loan" .)