Put out that loud bee - quickly! (2,3,6)
I believe the answer is:
at the double
'quickly' is the definition.
(I've seen this before)
'put out that loud bee' is the wordplay.
'put out' is an anagram indicator.
'that'+'loud'+'bee'='thatloudbee'
'thatloudbee' is an anagram of 'AT THE DOUBLE'.
(Other definitions for at the double that I've seen before include "dart ultimately aimed here?" , "in half the usual time?" , "Where arrow is aimed, initially" , "Where darts player aims to finish" , "travelling very fast" .)