Certainly hurry to consume whisky in former days (10)
I believe the answer is:
Here is my best explanation:
'certainly hurry to consume whisky in former days' is the definition.
I can't judge whether this defines the answer.
'certainly hurry to consume whisky' is the subsidiary indication.
'certainly' becomes 'yes' (I've seen this before).
'hurry' becomes 'tear' (tear is a kind of hurry**).
'to consume' means one lot of letters goes inside another.
'whisky' becomes 'rye' (rye is a kind of whisky).
'tear' enclosing 'rye' is 'teryear'.
(Other definitions for yesteryear that I've seen before include "Days gone by", "Days of old (poet.)", "Old", "Former times", "In the past", "Period 14 [CENTENARIAN] lived through", "Rossetti's translation questioned whereabouts of its snows!", "Time disappeared", "former times" and "Twelve months ago".)