Name available for suitable type of organisation (3-6)
I believe the answer is:
non-profit
'type of organisation' is the definition.
I know nothing about this answer so I can't judge whether this works.
'name available for suitable' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'available' becomes 'on' (I've seen this in other clues).
'for' becomes 'pro' (as in being 'pro' something).
'suitable' becomes 'fit' (similar in meaning).
'n'+'on'+'pro'+'fit'='NON-PROFIT'
Can you help me to learn more?
(Other definitions for non-profit that I've seen before include "Uncommercial" , "characterising a charity?" .)