Spooner's lecturer on fish brains (10)

I believe the answer is:

ringleader

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'fish brains' is the definition.
'ringleader' can be an answer for 'brains' (I've seen this before). I'm not certain of the 'fish' bit.

'spooner's lecturer on' is the wordplay.
'spooner' becomes 'ingl' (I can't explain this - if you can you should give a lot more credence to this answer).
'lecturer' becomes 'reader' (synonyms).
'on' indicates putting letters inside (as in clothing 'on' a person).
'ingl' going inside 'reader' is 'RINGLEADER'.

Can you help me to learn more?

(Other definitions for ringleader that I've seen before include "firebrand" , "Chief mischief maker" , "Mastermind" , "Main villain" , "Chief mischief-maker" .)

I've seen this clue in The Telegraph.

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