For instance, possibly all out to be legitimate (5)
I believe the answer is:
legal
'be legitimate' is the definition.
(associated in meaning)
'for instance possibly all out' is the wordplay.
'for instance' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'possibly' is an anagram indicator.
'out' indicates putting letters inside.
'all' with letters rearranged gives 'lal'.
'eg' placed inside 'lal' is 'LEGAL'.
'to' acts as a link.
(Other definitions for legal that I've seen before include "within the rules" , "right" , "Permitted by law" , "Authorised" , "Compliant with the law" .)