Gorge on pounds with few calories for heavenly body (9)
I believe the answer is:
satellite
'for heavenly body' is the definition.
(satellite is a kind of heavenly body)
'gorge on pounds with few calories' is the wordplay.
'gorge' becomes 'sate' (to sate oneself is to gorge on food).
'on' means one lot of letters go next to another.
'pounds' becomes 'L' (L can represent the monetary pound).
'with few calories' becomes 'lite' (lite can mean low in calories).
'sate'+'l'+'lite'='SATELLITE'
(Other definitions for satellite that I've seen before include "Communication device" , "Heavenly body revolving around a planet" , "Space traveller" , "outpost" , "Subordinate" .)