Occasionally, ditches in a higher place freeze over (3,2)

I believe the answer is:

ice up

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'freeze over' is the definition.
(I've seen this before)

'occasionally ditches in a higher place' is the wordplay.
'occasionally' indicates alternate letters.
'in a higher place' becomes 'up' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The alternating letters of 'ditches' are 'ice'.
'ice'+'up'='ICE UP'

Can you help me to learn more?

(Other definitions for ice up that I've seen before include "get coat" , "become frozen" , "Completely freeze" .)

I've seen this clue in The Telegraph.

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