Detective Sergeant apprehending former suspect in low spirits (8)
I believe the answer is:
doldrums
'low spirits' is the definition.
(I've seen this before)
'detective sergeant apprehending former suspect' is the wordplay.
'detective sergeant' becomes 'DS' (abbreviation for detective sergeant).
'apprehending' indicates putting letters inside.
'former' becomes 'old' (both can mean previous).
'suspect' becomes 'rum' (I've seen this in other clues).
'old'+'rum'='oldrum'
'ds' placed around 'oldrum' is 'DOLDRUMS'.
'in' acts as a link.
(Other definitions for doldrums that I've seen before include "Belt of calms in equatorial oceans" , "Belt of ocean calm" , "Belt of calm where winds from north and south come together" , "State of inactivity or stagnation" , "Ocean regions near equator with little or no wind" .)