Left out “a nut I caught, from the asylum” (7)

I believe the answer is:

lunatic

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'the asylum' is the definition.
(thesaurus)

'left out a nut i caught from' is the wordplay.
'left' becomes 'l' (common abbreviation).
'out' indicates anagramming the letters.
'i' becomes 'a'.
'caught from' becomes 'ic' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'nut'+'a'='nuta'
'nuta' with letters rearranged gives 'unat'.
'l'+'unat'+'ic'='LUNATIC'

Can you help me to learn more?

(Other definitions for lunatic that I've seen before include "Mad" , "crazed?" , "bananas" , "Crazy" , "fruitcake" .)

I've seen this clue in the Evening Standard.

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