Swallow one strong drink (7)
I believe the answer is:
martini
'strong drink' is the definition.
'martini' can be an answer for 'drink' (martini is a kind of drink). I am unsure of the 'strong' bit.
'swallow one' is the wordplay.
'swallow' becomes 'martin' (martin is a kind of swallow).
'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 "Italian drink" , "Cocktail of gin and dry vermouth" , "alcoholic drink" , "obtained from a bottle" , "rifle" .)