Vision certainly accepted by rowers? (8)
I believe the answer is:
eyesight
'vision' is the definition.
(eyesight is a kind of vision)
'certainly accepted by rowers?' is the wordplay.
'certainly' becomes 'yes' (I've seen this before).
'accepted by' means one lot of letters goes inside another.
'rowers?' becomes 'eight' (I've seen this before).
'yes' inserted inside 'eight' is 'EYESIGHT'.
(Other definitions for eyesight that I've seen before include "perception" , "Perceptive faculty" , "Requirement to look" , "Seeing faculty" , "Ability to see" .)