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