Haughty expert unfairly derided beginners (5)
I believe the answer is:
proud
'haughty' is the definition.
(similar in meaning)
'expert unfairly derided beginners' is the wordplay.
'expert' becomes 'pro' (short for professional).
'beginners' suggests taking the first letters.
The initial letters of 'unfairly derided' is 'ud'.
'pro'+'ud'='PROUD'
(Other definitions for proud that I've seen before include "Stuck-up" , "Walking tall" , "Haughty - sticking out" , "With high self-opinion" , "Self-satisfied - stately - protruding" .)