Turn away 50% of travellers in distress (5)
I believe the answer is:
avert
'turn away' is the definition.
(synonyms)
'50% of travellers in distress' is the wordplay.
'50% of' suggests halving the letters.
'in distress' indicates anagramming the letters.
'travellers' halved is 'trave'.
'trave' with letters rearranged gives 'AVERT'.
(Other definitions for avert that I've seen before include "Stop" , "With prominent incisors" , "Turn aside, prevent" , "Ward off (bad event)" , "Turn away (ones eyes)" .)