Name of chap taking one drink (7)
I believe the answer is:
martini
'drink' is the definition.
(martini is a kind of drink)
'name of chap taking one' is the wordplay.
'name of chap' becomes 'martin' (I can't justify this - if you can you should believe this answer much more).
'taking' is a charade indicator (letters next to each other).
'one' becomes 'I' (Roman numeral).
'martin'+'i'='MARTINI'
Can you help me to learn more?
(Other definitions for martini that I've seen before include "obtained from a bottle" , "rifle" , "Sienese painter" , "Type of Italian vermouth" , "Alternative name for Simone Memmi, pre-Renaissance Italian painter" .)