Snake's head twisted to and fro, in a way (4,2)
I believe the answer is:
sort of
'in a way' is the definition.
(I've seen this before)
'snake's head twisted to and fro' is the wordplay.
'head' suggests taking the first letters.
'twisted' is an anagram indicator.
'and' is a charade indicator (letters next to each other) (I've seen this in other clues).
The initial letter of 'snakes' is 's'.
'to' put after 'fro' is 'froto'.
'froto' with letters rearranged gives 'ortof'.
's'+'ortof'='SORT OF'
(Other definitions for sort of that I've seen before include "in a way" , "Not exactly" , "Somewhat" , "Not quite, but almost" , "Possibly, to an extent" .)