Prime order with one large risk (7)
I believe the answer is:
imperil
'risk' is the definition.
(I've seen this in another clue)
'prime order with one large' is the wordplay.
'order with' indicates anagramming the letters.
'one' becomes 'i' (Roman numeral).
'large' becomes 'L' (eg in clothes sizes).
'prime' with its letters mixed up with 'i' can make 'imperi'.
'imperi'+'l'='IMPERIL'
(Other definitions for imperil that I've seen before include "put at hazard" , "Place in danger" , "Put at risk" , "Jeopardize" , "Threaten, jeopardise" .)