Check steps - assuming foxtrot (6)
I believe the answer is:
stifle
'check' is the definition.
(I've seen this in another clue)
'steps assuming foxtrot' is the wordplay.
'steps' becomes 'stile' (I've seen this in other clues).
'assuming' indicates putting letters inside (inserted letters are taken in or assumed).
'foxtrot' becomes 'f' (phonetic alphabet: alpha, bravo, charlie etc.).
'stile' enclosing 'f' is 'STIFLE'.
(Other definitions for stifle that I've seen before include "Smother, check" , "Curb" , "Smother - 6 down (anag)" , "Repress, choke" , "Asphyxiate - itself (anag)" .)