Crossword Genius

As a bowler's jettisoned with little justification? (2,3,4,2,1,3)

Ross

I believe the answer is:

at the drop of a hat

I'm a little stuck... Click here to teach me more about this clue!

'jettisoned with little justification?' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'as a bowler's' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
'bowler' could be 'hat' (I've seen this in other clues) and 'hat' is found within the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for at the drop of a hat that I've seen before include "Derby's relegation signalled thus" , "When a tile descends" , "When a tile falls to the ground" , "in no time at all" , "without good reason?" .)

I've seen this clue in The Telegraph.
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