Cry because a book end's missing? (3)
I believe the answer is:
boo
'cry' is the definition.
(I have seen 'Cry of contempt ' mean 'boo' so perhaps 'cry' could also mean 'boo')
'because a book end's missing?' is the wordplay.
I cannot quite see how this works, but
'book' could be 'b' (abbreviation for book) and 'b' is found within the answer.
The remaining letters 'oo' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for boo that I've seen before include "A shocking exclamation!" , "Surprising outburst" , "Disapproving sound" , "Voice disapproval" , "Surprising exclamation" .)