One working out cries uncontrollably after river run (9)
I believe the answer is:
exerciser
'one working out' is the definition.
(a person who works out or exercises)
'cries uncontrollably after river run' is the wordplay.
'uncontrollably' indicates an anagram (I've seen this in other clues).
'after' means one lot of letters go next to another.
'river' becomes 'exe' (River Exe**).
'run' becomes 'r' (cricket abbreviation).
'cries' anagrammed gives 'rcise'.
'rcise' after 'exe' is 'exercise'.
'exercise'+'r'='EXERCISER'
(Other definitions for exerciser that I've seen before include "One keeping fit" , "swimmer, perhaps" , "Fitness fanatic" , "Gym member" , "Person working out" .)