Just a couple of solutions which I don't follow:
3d) 12 regularly nipping out into town (4)
N-O-
must be "noon". Twelve noon.
12a is "tool", but I don't think it applies to this clue.
21d) Twelve and a half foot seal (6)
C-I-C-
Must be "clinch"?
12a is "tool", but I don't think it applies to this clue.
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