Watch old boy dish up (7)
I believe the answer is:
observe
'watch' is the definition.
(observing is a kind of watching)
'old boy dish up' is the wordplay.
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'dish up' becomes 'serve' (synonyms).
'ob'+'serve'='OBSERVE'
(Other definitions for observe that I've seen before include "Watch carefully" , "Look at" , "What this newspaper does?" , "Keep - watch" , "Notice; study" .)