Ribbon suspended initially on tree (4)
I believe the answer is:
sash
'ribbon' is the definition.
(I've seen this before)
'suspended initially on tree' is the wordplay.
'initially' suggests taking the first letters.
'on' says to put letters next to each other.
'tree' becomes 'ash' (ash is a kind of tree).
The first letter of 'suspended' is 's'.
's'+'ash'='SASH'
(Other definitions for sash that I've seen before include "Sliding window frame" , "Frame for a windowpane" , "Window frame; silk band" , "Window frame - shoulder band" , "seen hanging around Miss World?" .)