Detective returns in subtle disguise (8)
I believe the answer is:
palliate
'disguise' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for palliate that I've seen before include "everything before I cut into spread" , "Mitigate (something bad)" , "Eat a pill (anag) - make easier" , "Allay" , "Soften (the effect of)" .)