Of tricks, it can have a number (3)
I believe the answer is:
box
'of tricks' is the definition.
The definition suggests a singular noun which matches the answer.
'it can have a number' is the wordplay.
I cannot really see how this works, but
'number' could be 'x' (X is an example) and 'x' is found in the answer.
The remaining letters 'bo' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for box that I've seen before include "Tackle defender" , "Spar; container" , "Wooden case" , "Topiary shrub" , "Christmas present" .)