Man’s coming in to look at oil-producing plant (6)
I believe the answer is:
sesame
'oil-producing plant' is the definition.
(I've seen this before)
'man's coming in to look' is the wordplay.
'man' becomes 'sam' ().
'coming in to' indicates putting letters inside.
'look' becomes 'see'.
'sam' placed within 'see' is 'SESAME'.
'at' acts as a link.
(Other definitions for sesame that I've seen before include "'Open - - !' (Ali Baba)" , "Oil-rich seed plant" , "Crop valued for its seeds and oil" , "Plant with edible seeds" , "Seeds producing an edible oil" .)