Replacement for one off their trolley, possibly: including second announcer (10)
I believe the answer is:
newscaster
'announcer' is the definition.
(I know that newscaster is a type of announcer)
'replacement for one off their trolley possibly including second' is the wordplay.
I cannot really understand how this works, but
'replacement' could be 'new' and 'new' is present in the answer.
'one' could be 'a' (a thing is one thing) and 'a' is found in the answer.
'second' could be 's' (common abbreviation) and 's' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for newscaster that I've seen before include "Baker, perhaps" , "who reads the headlines?" , "TV presenter" , "TV regular" .)