When you like, the tailor will make it up for you (2,4)
I believe the answer is:
at will
'when' is the definition.
Both the definition and answer are adverbs. Maybe they are linked in a way I don't understand?
'you like the tailor will make it up for you' is the wordplay.
I cannot quite understand how this works, but
'will' could be 'll' and 'll' is present in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for at will that I've seen before include "when one wants" , "Whenever one pleases, own choice" , "Fire .. .... - whenever you're ready" , "As one chooses" , "whenever you want" .)