Tendon is put back in original condition (5)
I believe the answer is:
sinew
'tendon' is the definition.
(I know that tendon can be written as sinew)
'is put back in original condition' is the wordplay.
'put back' shows that the letters should be reversed in order.
'in original condition' becomes 'new' (I can't explain this - if you can you should give a lot more credence to this answer).
'is' backwards is 'si'.
'si'+'new'='SINEW'
Can you help me to learn more?
(Other definitions for sinew that I've seen before include "Cord of tissue connecting muscle to bone" , "fibre" , "Force" , "As synonym for 'strength'" , "Muscular strength" .)