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 quite understand how this works, but
'hot' could be 'in' (both can mean fashionable) and 'in' is found within the answer.
This explanation may well be incorrect...

'of' acts as a link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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