What makes you ask questions about the collector's item? (9)
I believe the answer is:
curiosity
'collector's item?' is the definition.
(collector's item is a kind of curiosity)
'what makes you ask questions about the' is the wordplay.
I cannot really see how this works, but
'you' could be 'u' (homophones) and 'u' is found within the answer.
'ask' could be 'o' and 'o' is found in the answer.
'about' could be 'c' (circa) and 'c' is located in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for curiosity that I've seen before include "Something unusual (that killed the cat?)" , "Strong desire to learn something" , "That's a strange thing" , "Killer of cat" , "Unusual object" .)