Bones grouped together thanks to a strain injury (5)
I believe the answer is:
tarsi
'bones' is the definition.
(bones of the foot)
'grouped together thanks to a strain injury' is the wordplay.
I cannot really understand how this works, but
'thanks' could be 'ta' (UK informal version of 'thank you') and 'ta' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tarsi that I've seen before include "collections of bones?" , "Ankle bones" , "parts of leg" , "Parts of skeleton" , "Foot bones" .)