Drink mother's ruin occasionally out of can (7)
I believe the answer is:
martini
'drink' is the definition.
(martini is a kind of drink)
'mother's ruin occasionally out of can' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'out of' indicates putting letters inside (some letters on the outside of others).
'can' becomes 'tin' (both are metal containers).
The alternate letters of 'ruin' are 'ri'.
'ri' going around 'tin' is 'rtini'.
'ma'+'rtini'='MARTINI'
(Other definitions for martini that I've seen before include "obtained from a bottle" , "Sienese painter" , "Type of Italian vermouth" , "Alternative name for Simone Memmi, pre-Renaissance Italian painter" , "Italian drink" .)