To keep going with the metal work, a second wind is essential (7,2)
I believe the answer is:
soldier on
'to keep going' is the definition.
(I've seen this before)
'metal work a second wind is essential' is the wordplay.
I cannot quite see how this works, but
'metal' could be 'er' (Er is an example) and 'er' is found in the answer.
'second' could be 's' (common abbreviation) and 's' is found within the answer.
This explanation may well be incorrect...
'with the' acts as a link.
Can you help me to learn more?
(Other definitions for soldier on that I've seen before include "keep going" , "Don't give up" , "Persist in spite of difficulties" , "... to bear up" , "plug away" .)