Boy admits disappearance of small dictionary (8)
I believe the answer is:
glossary
'small dictionary' is the definition.
'glossary' can be an answer for 'dictionary' (I've seen this in another clue). I am unsure of the 'small' bit.
'boy admits disappearance' is the wordplay.
'boy' becomes 'gary' ().
'admits' is an insertion indicator (to admit is to allow in).
'disappearance' becomes 'loss' (I've seen this before).
'gary' placed around 'loss' is 'GLOSSARY'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for glossary that I've seen before include "List of terms text uses" , "Alphabetical list of technical terms" , "List of explanations of words" , "List of words pertaining to a subject" , "List of technical words with definitions" .)