Get beneath part of stadium (10)
I believe the answer is:
understand
'get' is the definition.
(I know that get can be written as understand)
'beneath part of stadium' is the wordplay.
'beneath' becomes 'under' (under means beneath or underneath).
'part of stadium' becomes 'stand' ('stand' is part of 'stadium').
'under'+'stand'='UNDERSTAND'
(Other definitions for understand that I've seen before include "Make sense of" , "Grasp - sympathise" , "Get the message" , "See" , "Perceive the meaning of" .)