Irritation, it's said, produced by small camp (15)
I believe the answer is:
dissatisfaction
'irritation' is the definition.
(thesaurus)
'it's said produced by small camp' is the wordplay.
'produced' indicates anagramming the letters.
'by' is a charade indicator (letters next to each other).
'small' becomes 's' (abbreviation - e.g. clothes size).
'camp' becomes 'faction' (faction is a kind of camp).
'its'+'said'='itssaid'
'itssaid' anagrammed gives 'dissati'.
'dissati'+'s'+'faction'='DISSATISFACTION'
(Other definitions for dissatisfaction that I've seen before include "Discontent; uneasiness" , "unhappiness" .)