Sign outside worker's shed (4-2)
I believe the answer is:
lean-to
'shed' is the definition.
(I've seen this before)
'sign outside worker's' is the wordplay.
'sign' becomes 'leo' (star sign).
'outside' means one lot of letters goes inside another (some letters go outside others).
'worker' becomes 'ant' (worker is a type of ant).
'leo' going around 'ant' is 'LEAN-TO'.
(Other definitions for lean-to that I've seen before include "Shed abutting other building" , "Outbuilding propped against another wall" , "Penthouse" , "Building built against another" , "Attached outbuilding" .)