Sitcom extraterrestrial (3)
I believe the answer is:
alf
'sitcom extraterrestrial' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alf that I've seen before include "Chap" , "Boy" , "- Ramsey, England manager in nineteen sixty six" , "See man" , "Sir - Ramsey, England footballer and manager" .)