Smile about the elm being damaged by a mischievous creature (7)
I believe the answer is:
gremlin
'a mischievous creature' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'smile about the elm being damaged' is the wordplay.
'smile' becomes 'grin' (grinning is a kind of smiling).
'about' is an insertion indicator.
'being damaged' indicates anagramming the letters.
'elm' with letters rearranged gives 'eml'.
'grin' enclosing 'eml' is 'GREMLIN'.
'by' is the link.
Can you help me to learn more?
(Other definitions for gremlin that I've seen before include "Imp causing mechanical problems?" , "cause of trouble for airmen" , "Mingler (anag.)" , "Mechanical fault" , "Mischievous troublemaker" .)