Carpenter's former increases announced (4)
I believe the answer is:
adze
'carpenter's former' is the definition.
(tool used by a carpenter to form things)
'increases announced' is the wordplay.
'increases' becomes 'adds' (to add to something is to increase it).
'announced' indicates a 'sounds like' (homophone) clue.
'adds' sounds like 'ADZE'.
(Other definitions for adze that I've seen before include "cutter" , "Wood cutting tool" , "Tool, sounds like sums" , "Something with sharp edge" , "One might cut" .)