Model entering beach to show stomach (5)
I believe the answer is:
stand
'stomach' is the definition.
(I know that stomach can be written as stand)
'model entering beach' is the wordplay.
'model' becomes 'T' (Ford Model T car).
'entering' indicates putting letters inside.
'beach' becomes 'sand'.
't' going into 'sand' is 'STAND'.
'to show' is the link.
(Other definitions for stand that I've seen before include "Pedestal" , "Set up" , "stick" , "Tolerate; rise" , "Support" .)