Sign of overconfidence from Surrey opener with tail (7)
I believe the answer is:
swagger
'sign of overconfidence' is the definition.
'surrey opener with tail' is the wordplay.
'opener' suggests taking the first letters.
'with' means one lot of letters go next to another.
'tail' becomes 'wagger' (something that wags).
The initial letter of 'surrey' is 's'.
's'+'wagger'='SWAGGER'
'from' acts as a link.
(Other definitions for swagger that I've seen before include "Boast" , "Show off" , "Walk proudly" , "Proud, pompous gait" , "Blustering arrogance" .)