One decent, if somehow flawed (9)
I believe the answer is:
deficient
'flawed' is the definition.
(thesaurus)
'one decent if somehow' is the wordplay.
'one' becomes 'i' (Roman numeral).
'somehow' indicates anagramming the letters.
'i'+'decent'+'if'='idecentif'
'idecentif' with letters rearranged gives 'DEFICIENT'.
(Other definitions for deficient that I've seen before include "less than complete" , "Inadequate" , "Lacking" .)