Most spruce home for birds including swallow (7)
I believe the answer is:
neatest
'most spruce' is the definition.
('neat' can be a synonym of 'spruce')
'home for birds including swallow' is the wordplay.
'home for birds' becomes 'nest' (I've seen this before).
'including' is an insertion indicator.
'swallow' becomes 'eat' (I've seen this in another clue).
'nest' enclosing 'eat' is 'NEATEST'.
(Other definitions for neatest that I've seen before include "Most orderly" , "best-looking desk, say?" , "Seat ten (anag)" , "Most smart" , "Most tidy" .)