Prime order - one large risk (7)
I believe the answer is:
imperil
'risk' is the definition.
(I've seen this before)
'prime order one large' is the wordplay.
'order' indicates anagramming the letters.
'one' becomes 'I' (Roman numeral).
'large' becomes 'L' (eg in clothes sizes).
'prime' anagrammed gives 'imper'.
'imper'+'i'+'l'='IMPERIL'
(Other definitions for imperil that I've seen before include "put at hazard" , "Place in danger" , "Expose" , "Put at risk" , "Endanger" .)