Pop producers putting sum of money on promotions (8)
I believe the answer is:
grandads
'pop producers' is the definition.
(fathers of fathers - pop can mean a father)
'sum of money on promotions' is the wordplay.
'sum of money' becomes 'grand' (a thousand pounds).
'on' is a charade indicator (letters next to each other).
'promotions' becomes 'ads' (ad is a kind of promotion).
'grand'+'ads'='GRANDADS'
'putting' acts as a link.
(Other definitions for grandads that I've seen before include "Old men having" , "Your mother and father's fathers" .)