Doctor inserted syringe's tip to have softening effect (9)
I believe the answer is:
tenderise
'to have softening effect' is the definition.
(to tenderise is to soften)
'doctor inserted syringe's tip' is the wordplay.
'doctor' indicates anagramming the letters.
'tip' says to take the final letters.
The last letter of 'syringe' is 'e'.
'inserted' anagrammed gives 'tenderis'.
'tenderis'+'e'='TENDERISE'
(Other definitions for tenderise that I've seen before include "pound" , "soften flesh" .)