Roofing contractor, say left in middle of row (5)
I believe the answer is:
tiler
'roofing contractor' is the definition.
(someone who tiles roofs)
'left in middle of row' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in middle of' indicates putting letters inside.
'row' becomes 'tier' (a tier is a row of things).
'l' put within 'tier' is 'TILER'.
'say' acts as a link.
(Other definitions for tiler that I've seen before include "Workman who fixes glazed rectangles in bathrooms" , "Roof-worker" , "Roof worker" , "doorkeeper at lodge" , "Working man" .)