Bottle up (6)
I believe the answer is:
stifle
'bottle up' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for stifle that I've seen before include "Repress - asphyxiate" , "Part of animal's leg" , "Have difficulty breathing" , "Smother, suffocate" , "Smother - 6 down (anag)" .)