Lastly, you mentioning occupational injury is threatening (4)
I believe the answer is:
ugly
'is threatening' is the definition.
(synonyms)
'lastly you mentioning occupational injury' is the wordplay.
'lastly' says to take the final letters.
The final letters of 'you mentioning occupational injury' are 'UGLY'.
(Other definitions for ugly that I've seen before include "Not nice-looking" , "Repulsive to the eye" , "Bad to look at" , "Not beautiful, plain" , "describe duckling thus" .)