3: Strangely enough, cat's lease keeps getting bigger (9)
 10: I catted around, in demand (7)
 11: Child is to depart, finally (3)
 12: Girl hatches subterfuge in prison tower (11)
 14: Expose to heat in opening of red-hot kiln (5)
 15: Bird dog bites boisterous lad (4,5)
 18: Civil libertarian sends building uprights (4,5)
 21: Perpendicular to 25-across? (5)
 22: Playwright rethinking copyright wrangle (4,7)
 25: Tweak with wrong end of a pin (3)
 26: Most poignant lament is written in French (7)
 27: Funny dame getting red (5)
 28: Drainage area cleaned around 43% of terrain (9)
 29: Cat, or what it does having lost its head (5)