Hardy character crossing river, swimmer with no trunks? (8)
I believe the answer is:
treeless
'with no trunks?' is the definition.
(with no tree trunks)
'hardy character crossing river swimmer' is the wordplay.
'hardy character' becomes 'tess' (I've seen this in another clue).
'crossing' means one lot of letters goes inside another.
'river' becomes 'r' (abbreviation for river).
'swimmer' becomes 'eel' (eel is a type of fish).
'r'+'eel'='reel'
'tess' going around 'reel' is 'TREELESS'.
(Other definitions for treeless that I've seen before include "Like the Arctic" , "As the Nullarbor Plain (if its name is to be believed)" , "Like a plain" , "like down, say" , "out of planes?" .)