It can turn into quite a lark (5)
I believe the answer is:
antic
'lark' is the definition.
(I've seen this in another clue)
'it can turn' is the wordplay.
'turn' is an anagram indicator.
'it'+'can'='itcan'
'itcan' is an anagram of 'ANTIC'.
'into quite a' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for antic that I've seen before include "Grotesque, fantastic (archaic)" , "Playful caper" , "seen to be bizarre, at one time" , "old buffoon" , "Mad act done for fun" .)