Waiter is devastated, making big bloomer (8)
I believe the answer is:
wisteria
'big bloomer' is the definition.
The definition suggests a singular noun which matches the answer.
'waiter is devastated' is the wordplay.
'devastated' indicates an anagram (devastate literally means destroy or lay waste to).
'waiter'+'is'='waiteris'
'waiteris' anagrammed gives 'WISTERIA'.
'making' acts as a link.
Can you help me to learn more?
(Other definitions for wisteria that I've seen before include "Climber" , "A flower, I swear it" , "Large climbing shrub, often attached to house" , "climbing plant" , "As I write badly about the flowering vine" .)