Welshman drinking French wine cold, as was Leonardo (2,5)
I believe the answer is:
da vinci
'as was leonardo' is the definition.
(Leonardo Da Vinci)
'welshman drinking french wine cold' is the wordplay.
'welshman' becomes 'dai' (Welsh name).
'drinking' indicates putting letters inside.
'french wine' becomes 'vin' ('wine' in French).
'cold' becomes 'c' (eg on taps).
'vin'+'c'='vinc'
'dai' placed around 'vinc' is 'DA VINCI'.
(Other definitions for da vinci that I've seen before include "Leonardo . . . painted the" , "Italian inventor artist" , "artist, scientist, and engineer" , "See 13 Down" , "'Versatile genius of the Italian Renaissance (2,5)'" .)