Crowded preserves in jars (3-6)
I believe the answer is:
jam-packed
'crowded preserves in jars' is the definition.
'jam packed' can be an answer for 'crowded' (thesaurus). I am not certain of the 'preserves in jars' bit.
'crowded preserves in' is the wordplay.
I cannot quite understand how this works, but
'crowded' could be 'packed' (packing is a kind of crowding) and 'packed' is located in the answer.
'preserves' could be 'jam' (jam is a kind of preserves) and 'jam' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for jam-packed that I've seen before include "Chock-a-block" , "Completely full" , "Heaving" , "Stuffed" , "Extremely crowded" .)