He may give guidance to eight men in a row (3)
I believe the answer is:
cox
'he may give guidance to eight men in a row' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is the entire clue.
Can you help me to learn more?
(Other definitions for cox that I've seen before include "Passenger vehicle" , "Member of rowing crew" , "Helmsman" , "Steerer of oarsmen in rowing boat" , "Boat's steerer" .)