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 jalapea-o' is the wordplay.
'in' indicates putting letters inside.
'enclosure' becomes 'pen' (pen is a kind of enclosure).
'with' is a charade indicator (letters next to each other).
'last bits of' says to take the final letters.
'jalapea-o' becomes 'o' (I can't justify this - if you can you should give a lot more credence to this answer).
The last letter of 'hot' is 't'.
'im' going within 'pen' is 'pimen'.
'pimen'+'t'+'o'='PIMENTO'
Can you help me to learn more?
(Other definitions for pimento that I've seen before include "Something spicy" , "Jamaica pepper" , "Sweet red pepper" , "Spicy berries" , "Plant" .)