Is water in them partly frozen? (7)
I believe the answer is:
sluices
'is' is the definition.
Although both the answer and definition are verbs in their -s form, I don't understand how they can define each other.
'water in them partly frozen?' is the wordplay.
I cannot quite understand how this works, but
'water' could be 'ice' (ice water is a kind of water) and 'ice' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
I've seen this clue in the Evening Standard.
Want a hint initially instead of a full solution?
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