Energy saved by the animal because of that (7)
I believe the answer is:
thereat
'because of that' is the definition.
I can't judge whether this defines the answer.
'energy saved by the animal' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mca).
'saved by' indicates putting letters inside (I've seen this in other clues).
'animal' becomes 'rat' (rat is a kind of animal).
'the'+'rat'='therat'
'e' put inside 'therat' is 'THEREAT'.
Can you help me to learn more?
(Other definitions for thereat that I've seen before include "At that point" , "On account of that" , "Theatre (anag)" , "At that place" .)