Grand seeing you on beach (8)
I believe the answer is:
thousand
'grand' is the definition.
('thousand' can be a synonym of 'grand')
'you on beach' is the wordplay.
'you' becomes 'thou' (I've seen this before).
'on' means one lot of letters go next to another.
'beach' becomes 'sand'.
'thou'+'sand'='THOUSAND'
'seeing' acts as a link.
(Other definitions for thousand that I've seen before include "Ten hundreds" , "Cardinal" , "See 1 down" , "cube" , "-- Island dressing" .)