Mothers embrace middle age and hot rock (5)

I believe the answer is:

magma

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

'hot rock' is the definition.
(I've seen this in another clue)

'mothers embrace middle age' is the wordplay.
'mothers' becomes 'mama' (I can't justify this - if you can you should give a lot more credence to this answer).
'embrace' is an insertion indicator.
'middle' indicates the central letters.
The centre of 'age' is 'g'.
'mama' going around 'g' is 'MAGMA'.

'and' is the link.

Can you help me to learn more?

(Other definitions for magma that I've seen before include "Semi-fluid material within the earth's crust" , "Lava" , "Molten rock in the earth's crust" , "hot stuff" , "Glassy volcanic rock" .)

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.