Free-rider might say wow at this, absurdly. (8)
I believe the answer is:
stowaway
'free-rider might say wow at this absurdly' is the definition.
The definition suggests a singular noun which matches the answer.
'say wow at this absurdly' is the wordplay.
'this absurdly' is an anagram indicator.
'say'+'wow'+'at'='saywowat'
'saywowat' with letters rearranged gives 'STOWAWAY'.
Can you help me to learn more?
(Other definitions for stowaway that I've seen before include "Person who hides aboard a ship to get free passage" , "Non-fare paying traveller at sea" , "One hiding aboard" , "Hidden passenger" , "One hides aboard ship to get free passage" .)