Spouse exercising for health (5,4)
I believe the answer is:
other half
'spouse' is the definition.
(informal term for a partner or spouse)
'exercising for health' is the wordplay.
'exercising' indicates anagramming the letters (letters exercise or move around).
'for'+'health'='forhealth'
'forhealth' anagrammed gives 'OTHER HALF'.
(Other definitions for other half that I've seen before include "partner" , "Spouse" , "Wife or hubby" , "people better off than us?" , "Dutch" .)