Girl Guide's teeth sure to wobble (9)
I believe the answer is:
usherette
'girl guide's' is the definition.
(I've seen this before)
'teeth sure to wobble' is the wordplay.
'to wobble' indicates an anagram (letters wobble around).
'teeth'+'sure'='teethsure'
'teethsure' anagrammed gives 'USHERETTE'.
(Other definitions for usherette that I've seen before include "Girl guide" , "Female theatre attendant" , "Person showing people to their seats" , "Cinema attendant" , "She shows people to seats" .)