Theatre worker quick with sign of hesitation (8)
I believe the answer is:
prompter
'theatre worker' is the definition.
(I've seen this before)
'quick with sign of hesitation' is the wordplay.
'quick' becomes 'prompt' (synonyms).
'with' means one lot of letters go next to another.
'sign of hesitation' becomes 'er'.
'prompt'+'er'='PROMPTER'
(Other definitions for prompter that I've seen before include "even more timely" , "more quickly?" , "I suggest" , "to be ready earlier" , "Helper of actors' memory" .)