Return googly but not wide “beamer” (8,3)
I believe the answer is:
electron gun
'beamer' is the definition.
(I've seen this before)
'return googly but not wide' is the wordplay.
'return' becomes 'elect' (I've seen this before).
'googly' becomes 'wrong 'un' (synonyms).
'but not' is a deletion indicator.
'wide' becomes 'w' (abbreviation e.g. in cricket).
'wrongun' with 'w' removed is 'rongun'.
'elect'+'rongun'='ELECTRON GUN'
(Other definitions for electron gun that I've seen before include "one producing beam?" , "Beamer" .)