Figures they may have to be filled (5)
I believe the answer is:
forms
'figures' is the definition.
('form' can be a synonym of 'figure')
'they may have to be filled' is the wordplay.
I cannot quite see how this works, but
'to' could be 'for' and 'for' is found within the answer.
The remaining letters 'ms' 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 forms that I've seen before include "Paperwork" , "beds for animals" , "Documents to be filled in" , "Takes shape" , "Benches" .)