Switches new ingredient for drinks (6)
I believe the answer is:
swings
'switches' is the definition.
(eg a swing voter switches their vote)
'new ingredient for drinks' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'ingredient for' is an insertion indicator.
'drinks' becomes 'swigs' (to take a swig is to take a drink).
'n' going within 'swigs' is 'SWINGS'.
(Other definitions for swings that I've seen before include "Moves to and fro like pendulum" , "What you lose on these, you hopefully gain on the roundabouts" , "Sways" , "What you lose on these, you'll gain on the roundabouts" , "Pieces of playground equipment" .)