Good person — most competent and most sane? (8)
I believe the answer is:
stablest
'most sane?' is the definition.
Both the definition and answer are superlative adjectives. Perhaps there's an association between them I don't understand?
'good person most competent' is the wordplay.
'good person' becomes 'st' (saint).
'most competent' becomes 'ablest' ('able' can be similar in meaning to 'competent').
'st'+'ablest'='STABLEST'
'and' is the link.
Can you help me to learn more?
(Other definitions for stablest that I've seen before include "Most unshakable" , "superlatively durable" , "most secure" .)