Work including reference for plant (7)
I believe the answer is:
trefoil
'plant' is the definition.
(trefoil is a kind of plant)
'work including reference' is the wordplay.
'work' becomes 'toil' (toil is a kind of work).
'including' indicates putting letters inside.
'reference' becomes 'ref' (I've seen this in other clues).
'toil' placed around 'ref' is 'TREFOIL'.
'for' acts as a link.
(Other definitions for trefoil that I've seen before include "A flower; three-lobe ornament" , "Three-leaf clover" , "Plant with leaves in three parts, eg clover" , "Plant with clover-like leaves" , "Loftier (anag) -- clover-like plant" .)