A growing source of flavouring for gin (7)
I believe the answer is:
juniper
'gin' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'a growing source of flavouring' is the wordplay.
I cannot quite see how this works, but
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'for' acts as a link.
Can you help me to learn more?
(Other definitions for juniper that I've seen before include "Plant producing berries used to flavour gin" , "kind of berries" , "Shrub flavouring gin" , "Its cones are used to flavour gin" , "Shrub providing flavour for gin" .)