Amazing biro, say, pocketed by academic without one (10)
I believe the answer is:
stupendous
'amazing' is the definition.
(thesaurus)
'biro say pocketed by academic without one' is the wordplay.
I cannot really see how this works, but
'biro say' could be 'pen' (biro is a kind of pen) and 'pen' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for stupendous that I've seen before include "Astounding" , "Phenomenal" , "Astoundingly huge" , "Extremely impressive" .)