Robbery not entirely legal, burglar reflected (4)
I believe the answer is:
'robbery' is the definition.
(I have seen 'violent robbery' mean 'blag' so perhaps 'robbery' could also mean 'blag')
'not entirely legal burglar reflected' is the wordplay.
'not entirely' indicates a hidden word.
'reflected' says the letters should be written in reverse.
'galb' is hidden in the letters of 'legal burglar'.
'galb' in reverse letter order is 'BLAG'.
(Other definitions for blag that I've seen before include "Lie to get something" , "Steal - wheedle" , "Cleverly obtain" , "Somehow obtain" , "Get something for free by lying" .)