Judge say recalled locking up old slaver (5)
I believe the answer is:
drool
'slaver' is the definition.
(I know that slaver can be written as drool)
'judge say recalled locking up old' is the wordplay.
'judge say' becomes 'lord' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'recalled' shows that the letters should be reversed in order (to recall can mean to bring something back).
'locking up' means one lot of letters goes inside another (I've seen this in other clues).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'lord' backwards is 'drol'.
'drol' going around 'o' is 'DROOL'.
Can you help me to learn more?
(Other definitions for drool that I've seen before include "Salivate" , "Dogs may" , "dribble" , "Show excitement" , "Let saliva run from the mouth" .)