Ill-suited f-flat cushions (5)
I believe the answer is:
unfit
'ill-suited' is the definition.
(I've seen this before)
'f-flat cushions' is the wordplay.
I cannot quite understand how this works, but
'f' is found in the answer.
The remaining letters 'unit' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for unfit that I've seen before include "Ill-equipped" , "Ill-suited" , "Inapt" , "Not prepared" , "Inappropriate" .)