Some flowers, irises, have a distinctive title (3)
I believe the answer is:
sir
'a distinctive title' is the definition.
'sir' can be an answer for 'title' (I've seen this before). I am not sure about the 'a distinctive' bit.
'some flowers irises have' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'SIR' is hidden in the letters of 'flowers irises have'.
Can you help me to learn more?
(Other definitions for sir that I've seen before include "Knight's prefix" , "Way to address gentleman" , "Polite term of address for a man" , "Title for knight or teacher" , "Title given to 10 Across" .)