Old woman, smarter, is fearsome creature (8)
I believe the answer is:
maneater
'fearsome creature' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'old woman smarter' is the wordplay.
'old woman' becomes 'ma' (I've seen this in other clues).
'smarter' becomes 'neater' ('neat' can be a synonym of 'smart').
'ma'+'neater'='MANEATER'
'is' is the link.
Can you help me to learn more?
(Other definitions for maneater that I've seen before include "Vamp" , "Highly-sexed, domineering woman" , "Tiger, say" , "Voracious woman!" .)