Stars gather round worker's outbuilding
I believe the answer is:
leanto
'outbuilding' is the definition.
(I've seen this before)
'stars gather round worker's' is the wordplay.
'stars' becomes 'leo' (I've seen this before).
'gather round' means one lot of letters goes inside another.
'worker' becomes 'ant' (worker is a type of ant).
'leo' enclosing 'ant' is 'LEAN-TO'.
(Other definitions for leanto that I've seen before include "shed" , "Roof" .)