Sign welcomes worker to shed (6)
I believe the answer is:
leanto
'shed' is the definition.
(I've seen this before)
'sign welcomes worker' is the wordplay.
'sign' becomes 'leo' (star sign).
'welcomes' indicates putting letters inside (in sense of 'invites in').
'worker' becomes 'ant' (worker is a type of ant).
'leo' placed around 'ant' is 'LEANTO'.
'to' acts as a link.
(Other definitions for leanto that I've seen before include "Roof" , "shed" .)