Degree covering energy and Newton's studies (4)
I believe the answer is:
dens
'studies' is the definition.
(I've seen this before)
'degree covering energy and newton's' is the wordplay.
'degree' becomes 'ds' (DS is an example**).
'covering' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mcs).
'and' is a charade indicator (letters next to each other).
'newton' becomes 'n' ('N' can be a synonym of 'newton').
'e'+'n'='en'
'ds' placed around 'en' is 'DENS'.
(Other definitions for dens that I've seen before include "Lairs" , "Habitats of some wild animals" , "Studies" , "Habitations of wild animals" , "Man's" .)