Upset if tan is faded (5)
I believe the answer is:
faint
'is faded' is the definition.
(thesaurus)
'upset if tan' is the wordplay.
'upset' indicates anagramming the letters.
'if'+'tan'='iftan'
'iftan' anagrammed gives 'FAINT'.
(Other definitions for faint that I've seen before include "dull" , "Weak" , "Swoon, lose consciousness" , "Barely perceptible" , "Swoon, pass out" .)