Dolly, perhaps, was 151? (5)
I believe the answer is:
clone
'dolly perhaps was' is the definition.
I don't understand the rest of the clue.
(Other definitions for clone that I've seen before include "Propagate asexually; copy" , "Identical copy" , "Exact replica" , "hacked phone" , "Plant or animal produced asexually from one parent" .)