Thinking of making yourself a hot drink? (7)

I believe the answer is:

mulling

I'm a little stuck... Click here to teach me more about this clue!

'thinking' is the definition.
(mulling is a kind of thinking)

'making yourself a hot drink?' is the wordplay.
I cannot really see how this works, but
'hot' could be 'in' (both can mean fashionable) and 'in' is present in the answer.
This explanation may well be incorrect...

'of' is the link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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