Jack is back on team after breaking bones (9)
I believe the answer is:
metatarsi
'bones' is the definition.
(I've seen this before)
'jack is back on team after breaking' is the wordplay.
'jack' becomes 'tar' (both are informal terms for sailor).
'back' says the letters should be written in reverse.
'on' says to put letters next to each other.
'after breaking' indicates an anagram.
'is' reversed gives 'si'.
'team' anagrammed gives 'meta'.
'tar'+'si'='tarsi'
'tarsi' after 'meta' is 'METATARSI'.
(Other definitions for metatarsi that I've seen before include "bones" , "Parts of the feet" .)