Maybe the rat took a ride to the theatre! (6)
I believe the answer is:
rodent
'maybe the rat took a ride' is the definition.
I can't tell whether this defines the answer.
'to the theatre' is the wordplay.
'to the' becomes 'rode' (I can't explain this - if you can you should believe this answer much more).
'theatre' becomes 'NT' (National Theatre).
'rode'+'nt'='RODENT'
Can you help me to learn more?
(Other definitions for rodent that I've seen before include "Small gnawing animal" , "Gnawing creature" , "Eg, mouse, squirrel" , "Mouse or squirrel, say" , "Small gnawing mammal" .)