Flasher on the coast amusing those at theatre (10)
I believe the answer is:
lighthouse
'flasher on the coast' is the definition.
'lighthouse' can be an answer for 'flasher' (something which flashes). I am not certain of the 'on the coast' bit.
'amusing those at theatre' is the wordplay.
I cannot quite see how this works, but
'amusing' could be 'light' (I've seen this before) and 'light' is present in the answer.
The remaining letters 'house' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lighthouse that I've seen before include "Warning feature for shipping" , "tower" , "It was a wonder" , "Tall structure emitting flashes to guide ships" , "Beamer" .)