Said to put in a grass border (7)
I believe the answer is:
reputed
'said' is the definition.
(thesaurus)
'in a grass border' is the wordplay.
'in' is an insertion indicator.
'a grass' becomes 'reed' (type of grass plant).
'border' becomes 'put' (I can't justify this - if you can you should give a lot more credence to this answer).
'reed' enclosing 'put' is 'REPUTED'.
'to put' is the link.
Can you help me to learn more?
(Other definitions for reputed that I've seen before include "Alleged" , "Erupted (anag)" , "Generally believed to exist" , "Rumoured, reckoned" , "Supposed" .)