V&A worker grabbing Greek's bum (7)
I believe the answer is:
vagrant
'bum' is the definition.
(I've seen this before)
'va worker grabbing greek's' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'grabbing' is an insertion indicator.
'greek' becomes 'gr' (abbreviation for Greek).
'va'+'ant'='vaant'
'vaant' going around 'gr' is 'VAGRANT'.
(Other definitions for vagrant that I've seen before include "Itinerant" , "Homeless wanderer" , "down-and-out" , "One with no fixed abode" , "Homeless person" .)