Danger irks terribly (4)
I believe the answer is:
risk
'danger' is the definition.
(I know that danger can be written as risk)
'irks terribly' is the wordplay.
'terribly' indicates anagramming the letters.
'irks' is an anagram of 'RISK'.
(Other definitions for risk that I've seen before include "dangerous thing" , "Gamble" , "Expose to danger" , "Danger or hazard" , "Jeopardy" .)