Madly keen to receive love, a source of energy (8)
I believe the answer is:
kerosene
'a source of energy' is the definition.
(kerosene is a fuel source)
'madly keen to receive love' is the wordplay.
'madly' indicates anagramming the letters.
'to receive' means one lot of letters goes inside another.
'love' becomes 'eros' (Greek god of love).
'keen' is an anagram of 'kene'.
'kene' enclosing 'eros' is 'KEROSENE'.
(Other definitions for kerosene that I've seen before include "Oil used as fuel in lamps and heaters" , "No seeker for American fuel oil" , "Sore knee (anag.)" , "Paraffin oil (E, not I)" , "Combustible" .)