Get involved with some painter, Venetian? (9)
I believe the answer is:
intervene
'get involved' is the definition.
(synonyms)
'with some painter venetian?' is the wordplay.
'with' says the answer is hidden in the clue.
'INTERVENE' is hidden within 'some painter venetian'.
(Other definitions for intervene that I've seen before include "Step in, become involved" , "Interfere, step in" , "Come between; interrupt" , "Mediate" , "Get involved so as to alter outcomes" .)