Somehow elm is so willowy? (7)
I believe the answer is:
lissome
'willowy?' is the definition.
(I've seen this before)
'somehow elm is so' is the wordplay.
'somehow' indicates anagramming the letters.
'elm'+'is'+'so'='elmisso'
'elmisso' is an anagram of 'LISSOME'.
(Other definitions for lissome that I've seen before include "Oil mess (anag)" , "Lithe; nimble" , "flexible" , "Slim, supple, graceful" , "So smile, being agile and lithe" .)