One of eight in a row? (3)
I believe the answer is:
oar
'one of eight in a row?' is the definition.
(eight can mean a rowing crew of eight rowers)
'of eight in a row?' is the wordplay.
'of' becomes 'o'.
'eight in a row?' becomes 'ar' (I am not sure about this - if you are sure you should believe this answer much more).
'o'+'ar'='OAR'
(Other definitions for oar that I've seen before include "Rowing device" , "Sportsman" , "One of an eight" , "Pole for rowing" , "Use it to move a boat" .)