To cheat, take passage both ways (6-5)
I believe the answer is:
double-cross
'to cheat' is the definition.
(thesaurus)
'take passage both ways' is the wordplay.
I cannot really see how this works, but
'take' could be 'do' (eg taking or doing drugs) and 'do' is present in the answer.
'passage' could be 'os' (os is a kind of passage) and 'os' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for double-cross that I've seen before include "Deceive, betray" , "Deceive supposed ally" , "Deceive (an ally, maybe)" , "Sell down the river" , "Betray - XX?" .)