They risk a lot of diversion and delays on vacation after hard border? (5,5)

'they risk a lot' is the definition.

'diversion and delays on vacation after hard border?' is the wordplay.
'diversion' becomes 'fun' (fun is a kind of diversion**).
'and' means one lot of letters go next to another.
'on vacation' suggests removing the centre.
'after' means one lot of letters go next to another.
'hard border?' becomes 'hedge'.
'delays' with its middle removed is 'ds'.
'fun' put next to 'ds' is 'funds'.
'funds' after 'hedge' is 'HEDGE FUNDS'.

'of' acts as a link.