Investigate stolen property ring involving family (4,4)
I believe the answer is:
look into
'investigate' is the definition.
('look into' can be a synonym of 'investigate')
'stolen property ring involving family' is the wordplay.
'stolen property' becomes 'loot' (loot is a kind of stolen property).
'ring' becomes 'o'.
'involving' means one lot of letters goes inside another.
'family' becomes 'kin' ('kin' can be a synonym of 'family').
'loot'+'o'='looto'
'looto' placed around 'kin' is 'LOOK INTO'.
(Other definitions for look into that I've seen before include "Try to discover the facts" , "Study" , "Investigate, explore" , "Enquire about, investigate" , "probe" .)