Puss returned within very short interval in good condition (6)
I believe the answer is:
intact
'short interval in good condition' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'puss returned within very' is the wordplay.
'puss' becomes 'cat' (I've seen this in other clues).
'returned' shows that the letters should be reversed in order.
'within' indicates putting letters inside.
'very' becomes 'int' (I am not sure about this - if you are sure you should believe this answer much more).
'cat' back-to-front is 'tac'.
'tac' placed within 'int' is 'INTACT'.
Can you help me to learn more?
(Other definitions for intact that I've seen before include "Whole - unbroken" , "Unscathed" , "Entire, undamaged" , "Flawless" , "Unbroken and unimpaired" .)