Good nutrient halved in Dr Pepper (8)
I believe the answer is:
pimiento
'pepper' is the definition.
(pimiento is a kind of pepper)
'good nutrient halved in dr' is the wordplay.
'good' becomes 'pi' (I've seen this in other clues).
'halved' suggests halving the letters.
'in' indicates putting letters inside.
'dr' becomes 'mo' (abbreviation for medical officer).
'nutrient' halved is 'ient'.
'ient' put within 'mo' is 'miento'.
'pi'+'miento'='PIMIENTO'
(Other definitions for pimiento that I've seen before include "Allspice" , "Red sweet pepper" , "Sweet red capsicum" , "Kitchen ingredient" , "What's sweet yet spicy" .)