Use announced for trees (4)
I believe the answer is:
yews
'trees' is the definition.
(yew is a kind of tree)
'use announced' is the wordplay.
'announced' indicates a 'sounds like' (homophone) clue.
'use' sounds like 'YEWS'.
'for' is the link.
(Other definitions for yews that I've seen before include "woods" , "traditional churchyard residents" , "Evergreen trees" .)