Rowers hope to develop measure of strength (10)
I believe the answer is:
horsepower
'measure of strength' is the definition.
(unit of power)
'rowers hope to develop' is the wordplay.
'to develop' indicates anagramming the letters.
'rowers'+'hope'='rowershope'
'rowershope' with letters rearranged gives 'HORSEPOWER'.
(Other definitions for horsepower that I've seen before include "Unit of power" , "Engine output measure" , "Rep who rose (anag) - equivalent of 745.7 watts" , "Measure of force" , "It's around seven hundred and fifty watts" .)