Slang for all to see reflected in a pub sign (9)
I believe the answer is:
autograph
'sign' is the definition.
(autographing is a kind of signing)
'slang for all to see reflected in a pub' is the wordplay.
'slang' becomes 'argot' ('argot' can be a synonym of 'slang'**).
'for all to see' becomes 'u' (universal dvd certificate).
'reflected' says the letters should be written in reverse.
'in' indicates putting letters inside.
'pub' becomes 'ph' (public house).
'argot'+'u'='argotu'
'argotu' backwards is 'utogra'.
'a'+'ph'='aph'
'utogra' placed inside 'aph' is 'AUTOGRAPH'.
(Other definitions for autograph that I've seen before include "A signature given as souvenir" , "Signer will give this" , "Famous person's signature" , "One's signature" , "Sign" .)