Swallowing a hot one will hurt (4)
I believe the answer is:
ache
'will hurt' is the definition.
'ache' can be an answer for 'hurt' (I've seen this in another clue). I am not sure about the 'will' bit.
'swallowing a hot one' is the wordplay.
'swallowing' is an insertion indicator.
'a hot' becomes 'h' (abbreviation eg on taps).
'one' becomes 'ace' (ace has a value of one in some card games).
'h' going into 'ace' is 'ACHE'.
Can you help me to learn more?
(Other definitions for ache that I've seen before include "Similar" , "painful" , "Nagging pain" , "Hanker" , "Dull continuous pain" .)