Supporter of glass company plant (7)
I believe the answer is:
coaster
'supporter of glass' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'company plant' is the wordplay.
'company' becomes 'co' (abbreviation).
'plant' becomes 'aster' (aster is a kind of plant).
'co'+'aster'='COASTER'
Can you help me to learn more?
(Other definitions for coaster that I've seen before include "It goes under a schooner, perhaps" , "Ship; (drinks) mat" , "on which some mug may be made to stand?" , "Small ship or beer mat" , "Mat to protect a table" .)