Voluntary work -- it set back loan being arranged (8)
I believe the answer is:
optional
'voluntary' is the definition.
(thesaurus)
'work it set back loan being arranged' is the wordplay.
'work' becomes 'op' (abbreviation for opus**).
'set back' shows that the letters should be reversed in order.
'being arranged' indicates anagramming the letters.
'it' backwards is 'ti'.
'loan' anagrammed gives 'onal'.
'op'+'ti'+'onal'='OPTIONAL'
(Other definitions for optional that I've seen before include "something extra?" , "Such as one can take or leave" , "Open to choice - take your pick" , "Not compulsory, discretionary" , "By choice, elective" .)