Did Catherine leave it with a groan, perhaps? (6)
I believe the answer is:
aragon
'did catherine leave it' is the definition.
I can't tell whether this defines the answer.
'with a groan perhaps?' is the wordplay.
'with' is an insertion indicator.
'perhaps?' indicates an anagram (I've seen 'perhaps' mean this).
'groan' is an anagram of 'argon'.
'a' put within 'argon' is 'ARAGON'.
Can you help me to learn more?
(Other definitions for aragon that I've seen before include "Old Spanish kingdom" , "Whence Catherine" , "part of Spain" , "(7 of) Henry's first" , "Former Spanish kingdom" .)