Criticise men on the radio, concealing their true appearance (8)
I believe the answer is:
disguise
'appearance' is the definition.
(disguise is a kind of appearance)
'criticise men on the radio' is the wordplay.
'criticise' becomes 'dis' (speak disrespectfully).
'men' becomes 'guys' (guy can informally mean a man).
'on the radio' indicates a 'sounds like' (homophone) clue.
'guys' sounds like 'guise'.
'dis'+'guise'='DISGUISE'
'concealing their true' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for disguise that I've seen before include "act of deception" , "Clothes etc misleading as to identity" , "Pretence" , "Misrepresent; costume" , "Camouflage to hide identity" .)