Form of energy transported uncle to a river (7)
I believe the answer is:
nuclear
'form of energy' is the definition.
'nuclear' can be an answer for 'energy' (nuclear energy is a kind of energy). I am not sure about the 'form of' bit.
'transported uncle to a river' is the wordplay.
'transported' is an anagram indicator.
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'river' becomes 'r' (abbreviation for river).
'uncle' put after 'a' is 'auncle'.
'auncle' with letters rearranged gives 'nuclea'.
'nuclea'+'r'='NUCLEAR'
Can you help me to learn more?
(Other definitions for nuclear that I've seen before include "kind of war" , "one's immediate family?" , "Relating to part of atom" , "Derived from fission or fusion" , "In sociology, of a family of parents and offspring only" .)