Clock at one perhaps - have a drink (8)
I believe the answer is:
cocktail
'a drink' is the definition.
(cocktail is a kind of drink)
'clock at one perhaps' is the wordplay.
'one' becomes 'i' (Roman numeral).
'perhaps' is an anagram indicator.
'clock'+'at'+'i'='clockati'
'clockati' with letters rearranged gives 'COCKTAIL'.
'have' is the link.
(Other definitions for cocktail that I've seen before include "Manhattan, for example" , "Screwdriver, for instance" , "old-fashioned in America" , "dish with prawn" , "Manhattan, perhaps" .)