Nothing quicker around ultimately than crane fly? (3,8)
I believe the answer is:
zip fastener
'fly?' is the definition.
(flies on trousers are zip fasteners)
'nothing quicker around ultimately than crane' is the wordplay.
'nothing' becomes 'zip' ('zip' can be a synonym of 'zero'**).
'quicker' becomes 'faster' ('faster' can be a synonym of 'quicker').
'around' is an insertion indicator.
'ultimately' says to take the final letters.
The last letters of 'than crane' are 'ne'.
'faster' placed around 'ne' is 'fastener'.
'zip'+'fastener'='ZIP-FASTENER'
(Other definitions for zip fastener that I've seen before include "Substitute for buttons" , "Flies" , "Locking device with two toothed edges and a sliding tab" , "It replaces buttons" .)