More like canal boat, quickly moved around with oar (8)
I believe the answer is:
narrower
'more like canal boat' is the definition.
'quickly moved around with oar' is the wordplay.
'quickly moved' becomes 'ran'.
'around' says the letters should be written in reverse.
'with' is a charade indicator (letters next to each other).
'oar' becomes 'rower' (an oar is something which 'rows').
'ran' backwards is 'nar'.
'nar'+'rower'='NARROWER'
(Other definitions for narrower that I've seen before include "Thinner" , "With less width" , "Less wide" .)