Healthy colour in resistance (3)
I believe the answer is:
tan
'healthy colour' is the definition.
'in resistance' is the wordplay.
'in' indicates a hidden word.
'TAN' is hidden within 'resistance'.
(Other definitions for tan that I've seen before include "Brownish colour" , "Process" , "Make black and blue" , "Turn hide into leather" , "belt" .)