Most important soldier on horse (9)

I believe the answer is:

paramount

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

'most important' is the definition.
(I've seen this in another clue)

'soldier on horse' is the wordplay.
'soldier' becomes 'para' (paratrooper).
'on horse' becomes 'mount' (mount is a kind of horse. I am not sure about the 'on' bit.).
'para'+'mount'='PARAMOUNT'

Can you help me to learn more?

(Other definitions for paramount that I've seen before include "First" , "More important than anything else" , "Sovereign" , "Predominant" , "Superior to all others" .)

I've seen this clue in The Times.

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