Old fellow fights in instances of disorderly behaviour (8)
I believe the answer is:
offences
'instances of disorderly behaviour' is the definition.
Although both the answer and definition are plural nouns, I don't understand how they can define each other.
'old fellow fights in' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'fellow' becomes 'F' (abbreviation - of a society etc.).
'fights' becomes 'fences' (fencing is a kind of fighting).
'in' is an insertion indicator.
'f' placed inside 'fences' is 'ffences'.
'o'+'ffences'='OFFENCES'
Can you help me to learn more?
(Other definitions for offences that I've seen before include "Misdemeanours" , "Trespasses" , "Illegal acts, breakings of the law" , "Breaches of the law" , "Crimes" .)