Part of problem is highlighted flaw (7)
I believe the answer is:
blemish
'flaw' is the definition.
(synonyms)
'part of problem is highlighted' is the wordplay.
'part of' indicates a hidden word.
'BLEMISH' is hidden in the letters of 'problem is highlighted'.
(Other definitions for blemish that I've seen before include "Stain - defect" , "deformity" , "Small flaw" , "acne?" , "Stain, flaw" .)