British like sportsmen losing large and being a real let-down (8)
I believe the answer is:
bathetic
'being a real let-down' is the definition.
(bathetic means underwhelming or anti-climactic)
'british like sportsmen losing large' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'like sportsmen' becomes 'athletic' (sportsmen are athletic).
'losing' suggests deleting specific letters.
'large' becomes 'L' (eg in clothes sizes).
'athletic' with 'l' removed is 'athetic'.
'b'+'athetic'='BATHETIC'
'and' acts as a link.
(Other definitions for bathetic that I've seen before include "causing anticlimax" , "sentimental" , "Anticlimactic" .)