Amount of energy produced by a recoil shot (7)
I believe the answer is:
calorie
'amount of energy' is the definition.
'calorie' can be an answer for 'amount' (calorie is a kind of amount). I'm not sure about the 'of energy' bit.
'by a recoil shot' is the wordplay.
'by' means one lot of letters go next to another.
'shot' is an anagram indicator.
'a' put after 'recoil' is 'recoila'.
'recoila' with letters rearranged gives 'CALORIE'.
'produced' is the link.
Can you help me to learn more?
(Other definitions for calorie that I've seen before include "Unit of heat energy" , "Oil race (anag)" , "Food energy unit" , "generating a bit of heat" , "Unit of energy in foods" .)