Rotating poster with illuminated frame moving back and forth (5)
I believe the answer is:
tidal
'moving back and forth' is the definition.
(like the tides)
'rotating poster with illuminated frame' is the wordplay.
'rotating' shows that the letters should be reversed in order.
'poster' becomes 'ad' (short for advert).
'with illuminated' becomes 'lit' (synonyms. I am not sure about the 'with' bit.).
'frame' is an insertion indicator.
'ad' put into 'lit' is 'ladit'.
'ladit' back-to-front is 'TIDAL'.
(Other definitions for tidal that I've seen before include "Concerning regular changes in sea level" , "Like waves" , "(Of the sea) ebbing and flowing" , "Of ebbs and flows" , "Subject to ebb and flow" .)