Crossword Genius

Go mad using only characters onboard ship - shall then do Fyffes bananas (3,3,3,6)

Ross

I believe the answer is:

fly off the handle

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

'do fyffes bananas' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'go mad using only characters onboard ship shall then' is the wordplay.
I cannot quite understand how this works, but
'go' could be 'fly' (flying is a kind of going) and 'fly' is located in the answer.
'then' could be 'and' (synonyms) and 'and' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for fly off the handle that I've seen before include "Lose one's temper" , "Robin perching on spade may" , "react angrily" , "See red" .)

I've seen this clue in The Independent.
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