Immediately suggestive of boater going down? (2,3,4,2,1,3)
I believe the answer is:
at the drop of a hat
'immediately' is the definition.
(I've seen this before)
'suggestive of boater going down?' is the wordplay.
I cannot quite understand how this works, but
'of' could be 'o' and 'o' is found in the answer.
'boater' could be 'hat' (I've seen this in another clue) and 'hat' is present in the answer.
'down?' could be 'd' and 'd' is located in 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 "without good reason?" , "just like that" , "Derby's relegation signalled thus" , "instantly" , "When pork pie downed" .)