Aunt short of time keeps mislabelled fruit machine (9)
I believe the answer is:
automaton
'machine' is the definition.
(I've seen this before)
'aunt short of time keeps mislabelled fruit' is the wordplay.
'short of' indicates named letters should be taken away.
'time' becomes 't' (abbreviation).
'keeps' means one lot of letters goes inside another (inserted letters are kept inside).
'mislabelled fruit' becomes 'tomato' (I can't justify this - if you can you should give a lot more credence to this answer).
'aunt' with 't' removed is 'aun'.
'aun' enclosing 'tomato' is 'AUTOMATON'.
Can you help me to learn more?
(Other definitions for automaton that I've seen before include "Robot figure" , "variety of android" , "being worked invariably" , "Mechanical figure" , "insensate being" .)