Mini mart's apparently keeping back smoked beef (8)
I believe the answer is:
pastrami
'smoked beef' is the definition.
(I've seen this before)
'mini mart's apparently keeping back' is the wordplay.
'keeping' says the answer is hidden in the clue.
'back' says the letters should be written in reverse.
'imartsap' is hidden within 'mini marts apparently'.
'imartsap' reversed gives 'PASTRAMI'.
(Other definitions for pastrami that I've seen before include "Spiced smoked beef" , "Spicy smoked beef" , "beef dish" , "smoked joint" , "Thinly sliced beef" .)