Stretch of water for which rower perhaps needs love and energy (4,4)
I believe the answer is:
blue nile
'stretch of water' is the definition.
(river)
'rower perhaps needs love and energy' is the wordplay.
'rower perhaps' becomes 'blue' (blue can mean an Oxford or Cambridge sportsperson).
'needs' says to put letters next to each other.
'love' becomes 'nil' (love and nil mean zero in cricket and football).
'and' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mc2).
'blue'+'nil'+'e'='BLUE NILE'
'for which' acts as a link.
(Other definitions for blue nile that I've seen before include "There's also a white river" , "African river" , "River flowing from Lake Tana (Ethiopia) to Khartoum (Sudan)" .)