Lift pig and howl playfully in mock combat (6,5)
I believe the answer is:
pillow fight
'mock combat' is the definition.
'lift pig and howl playfully' is the wordplay.
'and' is a charade indicator (letters next to each other).
'playfully' indicates anagramming the letters (I've seen this in other clues).
'lift'+'pig'+'howl'='liftpighowl'
'liftpighowl' anagrammed gives 'PILLOW-FIGHT'.
'in' is the link.
(Other definitions for pillow fight that I've seen before include "Mock battle in bedroom" , "Dormitory battle" , "Bedroom conflict" , "Bedroom battle (where feathers fly?)" .)