Firm punishment given by teacher? Bad luck (4,5)
I believe the answer is:
hard lines
'bad luck' is the definition.
(phrase used to express commiserations or sympathy)
'firm punishment given by' is the wordplay.
'firm' becomes 'hard' (both can mean durable or strong).
'punishment' becomes 'lines' (writing the same thing over and over).
'given by' means one lot of letters go next to another.
'hard'+'lines'='HARD LINES'
'teacher?' is the link.
This may not be correct. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for hard lines that I've seen before include "Script full of tongue-twisters?" , "Tough" , "Bad luck" .)