Elderly paid with flies (4)
I believe the answer is:
aged
'elderly' is the definition.
(synonyms)
'paid with flies' is the wordplay.
'paid' becomes 'waged' (paid with a wage).
'with' becomes 'w' (abbreviation).
'flies' indicates named letters should be taken away (some letters fly away).
'waged' with 'w' taken out is 'AGED'.
(Other definitions for aged that I've seen before include "Got older" , "Elderly" , "way over the hill" , "Became older" , "Matured like wine in wood" .)