That moon forced energy out (3,2,4)
I believe the answer is:
not at home
'out' is the definition.
(I've seen this in another clue)
'that moon forced energy' is the wordplay.
'forced' is an anagram indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'that'+'moon'='thatmoon'
'thatmoon' is an anagram of 'notathom'.
'notathom'+'e'='NOT AT HOME'
(Other definitions for not at home that I've seen before include "barking at the moon" , "Ignoring visitors" .)