Briefly turned air down (2,1,4)
I believe the answer is:
in a word
'briefly' is the definition.
(I've seen this in another clue)
'turned air down' is the wordplay.
'turned' is an anagram indicator.
'air'+'down'='airdown'
'airdown' is an anagram of 'IN A WORD'.
(Other definitions for in a word that I've seen before include "summing up" , "To summarize" , "concise" , "Where letters are usually found" , "To summarise (the shortest way possible!)" .)