Row about learner, one working on roof? (5)
I believe the answer is:
tiler
'one working on roof?' is the definition.
(someone who tiles roofs)
'row about learner' is the wordplay.
'row' becomes 'tier' (a tier is a row of things).
'about' means one lot of letters goes inside another.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'tier' going around 'l' is 'TILER'.
(Other definitions for tiler that I've seen before include "Worker who lays small squares" , "Roof worker" , "Working man" , "doorkeeper at lodge" , "Craftsman" .)