However unsuitable, it's about to take a rest (5)
I believe the answer is:
inapt
'however unsuitable' is the definition.
'inapt' can be an answer for 'unsuitable' (I've seen this before). I am unsure of the 'however' bit.
'about to take a rest' is the wordplay.
'about to' becomes 'it' (I am not sure about this - if you are sure you should believe this answer much more).
'take' indicates putting letters inside.
'a rest' becomes 'nap' (I've seen this in another clue).
'it' going around 'nap' is 'INAPT'.
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for inapt that I've seen before include "Unsuited" , "not seemly" , "Not fit, unsuitable" , "Far from fit" , "Ill-chosen, not suitable" .)