Shocks for old man turning up with chums (6)
I believe the answer is:
appals
'shocks' is the definition.
('appal' can be a synonym of 'shock')
'old man turning up with chums' is the wordplay.
'old man' becomes 'pa' (both can mean someone's father).
'turning up' is a reversal indicator.
'with' is a charade indicator (letters next to each other).
'chums' becomes 'pals' ('pal' can be a synonym of 'chum').
'pa' written backwards gives 'ap'.
'ap'+'pals'='APPALS'
'for' acts as a link.
(Other definitions for appals that I've seen before include "'Horrifies, outrages (6)'" , "Shocks" , "Fills with disgust" , "Fills with dismay or horror (6)" .)