Boy clutching twisted ankle in English national park (8)
I believe the answer is:
lakeland
'english national park' is the definition.
(Lake District National Park)
'boy clutching twisted ankle' is the wordplay.
'boy' becomes 'lad' (informal term for boy).
'clutching' is an insertion indicator.
'twisted' indicates anagramming the letters.
'ankle' is an anagram of 'kelan'.
'lad' enclosing 'kelan' is 'LAKELAND'.
'in' acts as a link.
(Other definitions for lakeland that I've seen before include "National park - kind of terrier" , "Region in Cumbria" .)