Crossword Genius

Relating to several terms in case about reversing on motorway (9)

Ross

I believe the answer is:

trinomial

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

'relating to several terms' is the definition.
I can't judge whether this definition defines the answer.

'case about reversing on motorway' is the wordplay.
'case' becomes 'trial' (court case).
'about' means one lot of letters goes inside another.
'reversing' is a reversal indicator.
'motorway' becomes 'MI' (resembles Mt, English motorway).
'on' in reverse letter order is 'no'.
'no'+'mi'='nomi'
'trial' going around 'nomi' is 'TRINOMIAL'.

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Times.
Want a hint initially instead of a full solution? Install my app