Press on trail of group hoping to form next government (13)

I believe the answer is:

shadowcabinet

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'group hoping to form next government' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'press on trail of' is the wordplay.
'press' becomes 'cabinet' (press can mean a cupboard).
'on' says to put letters next to each other.
'trail of' becomes 'shadow' (I can't justify this - if you can you should believe this answer much more).
'cabinet' put after 'shadow' is 'SHADOWCABINET'.

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I've seen this clue in The Irish Times.

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