Supposed to have place in plant (7)
I believe the answer is:
reputed
'supposed' is the definition.
(I've seen this in another clue)
'place in plant' is the wordplay.
'place' becomes 'put' (synonyms).
'in' is an insertion indicator.
'plant' becomes 'reed' (reed is a kind of plant).
'put' put into 'reed' is 'REPUTED'.
'to have' acts as a link.
(Other definitions for reputed that I've seen before include "Generally believed (to be the case)" , "Deemed" , "Erupted (anag)" , "Supposed" , "Regarded as such" .)