Trouble, fiery occasionally, with sex in part (10)

I believe the answer is:

irritation

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'trouble' is the definition.
(thesaurus)

'fiery occasionally with sex in part' is the wordplay.
'occasionally' indicates alternate letters.
'with' indicates putting letters inside.
'sex' becomes 'it' (a common euphemism).
'in part' becomes 'ration' (ration is a kind of part. I am not sure about the 'in' bit.).
The alternate letters of 'fiery' are 'ir'.
'it' inserted within 'ration' is 'ritation'.
'ir'+'ritation'='IRRITATION'

Can you help me to learn more?

(Other definitions for irritation that I've seen before include "nuisance" , "Annoyance, anger" .)

I've seen this clue in The Telegraph.

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