Large title? Unexpectedly tiny! (6)
I believe the answer is:
little
'tiny' is the definition.
(similar in meaning)
'large title? unexpectedly' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'unexpectedly' indicates an anagram.
'title' anagrammed gives 'ittle'.
'l'+'ittle'='LITTLE'
(Other definitions for little that I've seen before include "Self-important authoritarian" , "Fairies and leprechauns?" , "Small in size or amount" , "Book by Dickens" , "Peanuts" .)