Asian climber in risky venture left without energy (5)
I believe the answer is:
betel
'asian climber' is the definition.
(I know that betel is a type of asian climber)
'risky venture left without energy' is the wordplay.
'risky venture' becomes 'bet'.
'left' becomes 'l' (common abbreviation).
'without' is an insertion indicator ('without' can be similar in meaning to 'outside').
'energy' becomes 'e' (physics symbol as in E=mc2).
'bet'+'l'='betl'
'betl' enclosing 'e' is 'BETEL'.
'in' acts as a link.
(Other definitions for betel that I've seen before include "Asian palm and nut" , "Narcotic leaf" , "climbing plant" , "Asian feather palm" , "Plant leaf chewed in the East" .)