A groom wasted energy, parking (7)
I believe the answer is:
moorage
'parking' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'a groom wasted energy' is the wordplay.
'wasted' indicates an anagram.
'energy' becomes 'e' (physics symbol as in E=mc2).
'a'+'groom'='agroom'
'agroom' is an anagram of 'moorag'.
'moorag'+'e'='MOORAGE'
Can you help me to learn more?
(Other definitions for moorage that I've seen before include "Place to fasten" , "Place for a ship to make fast" , "Berthing fee" , "Charge for tying up a ship" , "Fee paid for tying up a boat" .)