Current of air upended the short beefeater? (7)
I believe the answer is:
draught
'current of air' is the definition.
(thesaurus)
'upended the short beefeater?' is the wordplay.
'upended' says the letters should be written in reverse (in a down clue, letters go up).
'short' means to remove the last letter.
'beefeater?' becomes 'guard' (Beefeater is a type of guard).
'the' with its last letter removed is 'th'.
'th'+'guard'='thguard'
'thguard' reversed gives 'DRAUGHT'.
(Other definitions for draught that I've seen before include "One short of cash feels this" , "It may be drunk" , "intake" , "Water depth; served from a cask" , "Dose of medicine" .)