Send up satellite, heading off in pursuit of light source (7)
I believe the answer is:
lampoon
'send up' is the definition.
(thesaurus)
'satellite heading off in pursuit of light source' is the wordplay.
'satellite' becomes 'moon' (moon is a kind of satellite).
'heading off' means to remove the first letter.
'in pursuit of' means one lot of letters go next to another (some letters chase after others).
'light source' becomes 'lamp' (I've seen this in another clue).
'moon' with its initial letter taken away is 'oon'.
'oon' put after 'lamp' is 'LAMPOON'.
(Other definitions for lampoon that I've seen before include "Ridicule in writing or verse" , "Satirical work" , "Make fun of" , "Satirise, ridicule" , "send-up" .)