I'd be inferior to Tim, being shy (5)
I believe the answer is:
timid
'being shy' is the definition.
('timid' can be a synonym of 'shy')
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for timid that I've seen before include "not forward" , "afraid to speak out?" , "Nervous and easily alarmed" , "Mouse" , "Easily alarmed, shy" .)