Give the thumbs up to hairstyle with sex appeal (6)
I believe the answer is:
permit
'give the thumbs up' is the definition.
Both the definition and answer are verbs in their base form.
Perhaps you can see a link between them that I can't see?
'hairstyle with sex appeal' is the wordplay.
'hairstyle' becomes 'perm' (perm is a kind of hairstyle).
'with' means one lot of letters go next to another.
'sex appeal' becomes 'it'.
'perm'+'it'='PERMIT'
'to' is the link.
Can you help me to learn more?
(Other definitions for permit that I've seen before include "Warrant" , "Officially allow" , "Let; enabling document" , "Allow, authorise" , "Official document giving authorisation" .)