I'm in enclosure with last bits of hot jalapeño pepper (7)
I believe the answer is:
pimento
'pepper' is the definition.
(pimiento is a type of pepper)
'i'm in enclosure with last bits of hot jalapeno' is the wordplay.
'in' is an insertion indicator.
'enclosure' becomes 'pen' (pen is a kind of enclosure).
'with' says to put letters next to each other.
'last bits of' suggests the final letters.
The last letters of 'hot jalapeno' are 'to'.
'im' inserted into 'pen' is 'pimen'.
'pimen'+'to'='PIMENTO'
(Other definitions for pimento that I've seen before include "Allspice - top mine (anag)" , "Sweet red pepper" , "Vegetable" , "Type of pepper" , "Something spicy" .)