The nerve of the little creature! It is brave! (7)
I believe the answer is:
gallant
'brave' is the definition.
(similar in meaning)
'the nerve of the little creature' is the wordplay.
'the nerve of' becomes 'gall' (I can't explain this - if you can you should believe this answer much more).
'the little creature' becomes 'ant'.
'gall'+'ant'='GALLANT'
'it is' is the link.
Can you help me to learn more?
(Other definitions for gallant that I've seen before include "Chivalrous - dashing" , "Dashing gentleman" , "Brave and chivalrous like knight of old" , "Brave, heroic" , "Heroic; chivalrous" .)