Aeroplane going round pole for a joke (4)
I believe the answer is:
jest
'a joke' is the definition.
(synonyms)
'aeroplane going round pole' is the wordplay.
'aeroplane' becomes 'jet' (jet is a kind of aeroplane).
'going round' means one lot of letters goes inside another (some letters go around others).
'pole' becomes 's' (abbreviation for South, as in South Pole).
'jet' placed around 's' is 'JEST'.
'for' acts as a link.
(Other definitions for jest that I've seen before include "` `Many a true word is spoken in . . . .' '" , "Banter, joke" , "Humorous remark" , "Quip" , "Joke, gag" .)