Sick of frills (3)
I believe the answer is:
ill
'sick' is the definition.
('ill' can be similar in meaning to 'sick')
'of frills' is the wordplay.
'of' says the answer is hidden in the clue.
'ILL' can be found hidden inside 'frills'.
(Other definitions for ill that I've seen before include "Not well, sick" , "Unwell from bacillus" , "poor" , "Wicked" , "Unwell, sick" .)