Very smart but initially a bit wet (6)
I believe the answer is:
brainy
'very smart but initially' is the definition.
I can't tell whether this definition defines the answer.
'a bit wet' is the wordplay.
'a bit' becomes 'b' (this might be a standard abbreviation of which I'm unaware).
'wet' becomes 'rainy' ('rainy' can be similar in meaning to 'wet').
'b'+'rainy'='BRAINY'
Can you help me to learn more?
(Other definitions for brainy that I've seen before include "Intellectual" , "Clever, got lots of grey matter" , "Showing intelligence" , "Intelligent, clever." , "smart?" .)