Do up laces after second set of exercises (6)
I believe the answer is:
scales
'set of exercises' is the definition.
'scales' can be an answer for 'set' (I have seen 'Set of balances ' mean 'scales' so perhaps 'set' could also mean 'scales'). I'm unsure of the 'of exercises' bit.
'do up laces after second' is the wordplay.
I cannot really understand how this works, but
an anagram of 'laces' is 'scale' which is present in the answer.
'second' could be 's' (common abbreviation) and 's' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for scales that I've seen before include "though it's not Pisces" , "Weighing devices or fish flakes" , "The practice of music" , "Set of balances" , "Fish flakes or measuring devices" .)