Charge about, arresting one or two (4)
I believe the answer is:
pair
'two' is the definition.
(pair is a kind of two)
'charge about arresting one' is the wordplay.
'charge' becomes 'rap' (I have seen 'Criminal charge ' mean 'rap' so perhaps 'charge' could also mean 'rap'**).
'about' shows that the letters should be reversed in order.
'arresting' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'rap' in reverse letter order is 'par'.
'par' enclosing 'i' is 'PAIR'.
'or' is the link.
(Other definitions for pair that I've seen before include "Set of two" , "Twosome" , "players of duet?" , "Husband and wife" , "Put together - two of a kind" .)