Serious wear in vest when all tops are removed (7)
I believe the answer is:
earnest
'serious' is the definition.
(similar in meaning)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for earnest that I've seen before include "Resolute" , "Art deserving" , "serious attention" , "Sincere -- humourless" , "Something of value to bind a contract" .)