“The Saint” unexpectedly wavering (8)
I believe the answer is:
'wavering' is the definition.
(wavering can mean hesitant or faltering)
'the saint unexpectedly' is the wordplay.
'unexpectedly' is an anagram indicator.
'thesaint' with letters rearranged gives 'HESITANT'.
(Other definitions for hesitant that I've seen before include "Indecisive" , "Uncertain, nervous" , "Reluctant, feeling indecision" , "Demurring" , "Diffident" .)