Support tip on rambling rose (7)
I believe the answer is:
endorse
'support' is the definition.
(synonyms)
'tip on rambling rose' is the wordplay.
'tip' becomes 'end' ().
'on' is an insertion indicator.
'rambling' indicates anagramming the letters.
'rose' with letters rearranged gives 'orse'.
'end' placed within 'orse' is 'ENDORSE'.
(Other definitions for endorse that I've seen before include "Favour" , "Publicly approve" , "Give public approval of (something)" , "Approve or underwrite" , "Put one's name to, approve" .)