Bats vanish after entrance of knight errant (7)
I believe the answer is:
knavish
'errant' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I don't see?
'bats vanish after entrance of knight' is the wordplay.
'bats' indicates anagramming the letters (slang for mad).
'after' says to put letters next to each other.
'entrance of' indicates taking the first letters.
The initial letter of 'knight' is 'k'.
'vanish' with letters rearranged gives 'navish'.
'navish' after 'k' is 'KNAVISH'.
Can you help me to learn more?
(Other definitions for knavish that I've seen before include "Wily" , "Full of dirty tricks" , "Villainous" , "Rascally" , "Fraudulent" .)