When, within a month, one's left, can't find (6)
I believe the answer is:
mislay
'one's left can't find' is the definition.
I can't judge whether this definition defines the answer.
'when within a month' is the wordplay.
'when' becomes 'isl' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'within' means one lot of letters goes inside another.
'a month' becomes 'May' (May is an example).
'isl' going inside 'may' is 'MISLAY'.
Can you help me to learn more?
(Other definitions for mislay that I've seen before include "Lose track of" , "Put in wrong place, lose temporarily" , "Put something aside and forget where" , "Lose (something)" , "Temporarily not find" .)