Harmful, detrimental (7)
I believe the answer is:
adverse
I believe this clue is a double definition.
'harmful' is the first definition.
(synonyms)
'detrimental' is the second definition.
(I've seen this before)
(Other definitions for adverse that I've seen before include "Unfavourable to evaders" , "'Contrary, untoward (7)'" , "Opposed to or unfavourable" , "Evaders being harmful" , "negative result" .)