Irish family group put off dividing spoils (8)
I believe the answer is:
corrupts
'spoils' is the definition.
(I know this)
'irish family group put off dividing' is the wordplay.
'irish family group' becomes 'Corrs' (The Corrs, Irish band made up of the Corr siblings).
'off' indicates anagramming the letters.
'dividing' means one lot of letters goes inside another (inserted letters divide the word).
'put' with letters rearranged gives 'upt'.
'corrs' going around 'upt' is 'CORRUPTS'.
(Another definition for corrupts that I've seen is " Debauches or contaminates".)