Scrutinise modern gal spreading gossip (13)
I believe the answer is:
scandalmonger
'gossip' is the definition.
(scandalmonger is a kind of gossip)
'scrutinise modern gal spreading' is the wordplay.
'scrutinise' becomes 'scan' (I've seen this before).
'spreading' is an anagram indicator.
'modern'+'gal'='moderngal'
'moderngal' with letters rearranged gives 'dalmonger'.
'scan'+'dalmonger'='SCANDALMONGER'
(Other definitions for scandalmonger that I've seen before include "Person spreading malicious gossip" , "Tattler" , "Spreader of rumours" , "Purveyor of dirt about others" , "Person spreading malicious tittle-tattle" .)