Intercept and trouble ambassador following repeated arrests (4,3)
I believe the answer is:
head off
'intercept' is the definition.
(I've seen this before)
'trouble ambassador following repeated arrests' is the wordplay.
'trouble' becomes 'ado' (both can mean bother or commotion).
'ambassador' becomes 'HE' (His or Her Excellency).
'following' becomes 'f' (used when citing page numbers etc).
'repeated' indicates the doubling of some letters.
'arrests' indicates putting letters inside (inserted letters are held or arrested).
'f' duplicated is 'ff'.
'he'+'ff'='heff'
'ado' inserted inside 'heff' is 'HEAD OFF'.
'and' is the link.
(Other definitions for head off that I've seen before include "go" , "like Robespierre?" , "Block" , "What Anne Boleyn eventually had" , "result of execution?" .)