Wrap boy's broken ankle with some kind of shirt (7)
I believe the answer is:
blanket
'wrap' is the definition.
(blanket can mean to wrap up)
'boy's broken ankle with some kind of shirt' is the wordplay.
'boy' becomes 'b' (abbreviation used in schools).
'broken' is an anagram indicator.
'with' says to put letters next to each other.
'some kind of shirt' becomes 'T' (T-shirt).
'ankle' anagrammed gives 'lanke'.
'b'+'lanke'+'t'='BLANKET'
(Other definitions for blanket that I've seen before include "General" , "Warm covering" , "Thick item on bed" , "coating" , "Mantle" .)