Exploit energy stored in adipose tissue (4)
I believe the answer is:
feat
'exploit' is the definition.
(I know that exploit can be written as feat)
'energy stored in adipose tissue' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mca).
'stored in' indicates putting letters inside.
'adipose tissue' becomes 'fat' (synonyms).
'e' inserted into 'fat' is 'FEAT'.
(Other definitions for feat that I've seen before include "An accomplishment of fate" , "Remarkable achievement of fate" , "Great deed" , "Notable act" , "Notable achievement" .)