Sharp, taking river to be strong (5)
I believe the answer is:
acrid
'be strong' is the definition.
(thesaurus)
'sharp taking river' is the wordplay.
'sharp' becomes 'acid' (as in sharp-tasting).
'taking' is an insertion indicator.
'river' becomes 'r' (abbreviation).
'acid' going around 'r' is 'ACRID'.
'to' acts as a link.
(Other definitions for acrid that I've seen before include "Strong and sharp-smelling" , "causing corrosion" , "Sharp-smelling like smoke" , "Bitter - pungent" , "Nastily pungent" .)