Male -- he's silly to become engaged (4)
I believe the answer is:
mesh
'become engaged' is the definition.
(to mesh is to interlink or become engaged)
'male he's silly' is the wordplay.
'male' becomes 'm' (common abbreviation).
'silly' indicates anagramming the letters.
'hes' with letters rearranged gives 'esh'.
'm'+'esh'='MESH'
'to' is the link.
(Other definitions for mesh that I've seen before include "Crossed wires" , "Interlock" , "Interweave - netting" , "Net fabric" , "Undeviating" .)