Like the energy of an eccentric uncle with a warm heart (7)
I believe the answer is:
nuclear
'like the energy of' is the definition.
I can't judge whether this defines the answer.
'eccentric uncle with a warm heart' is the wordplay.
'eccentric' indicates anagramming the letters.
'with' says to put letters next to each other.
'heart' says to take the centre.
The middle letters of 'warm' are 'ar'.
'uncle' anagrammed gives 'nucle'.
'nucle'+'ar'='NUCLEAR'
'an' is the link.
Can you help me to learn more?
(Other definitions for nuclear that I've seen before include "Derived from fission or fusion" , "With dangerous weapons" , "Involving part of an atom" , "Relating to part of atom" , "Relating to atomic structure" .)