Reproduction Stonehenge assembled in capital (15)
I believe the answer is:
parthenogenesis
'reproduction' is the definition.
(parthenogenesis is a kind of reproduction)
'stonehenge assembled in capital' is the wordplay.
'assembled' indicates an anagram.
'in' is an insertion indicator.
'capital' becomes 'paris' (capital of France).
'stonehenge' with letters rearranged gives 'thenogenes'.
'thenogenes' going within 'paris' is 'PARTHENOGENESIS'.
(Other definitions for parthenogenesis that I've seen before include "Means to reproduce" , "Way of making young" , "virgin birth" .)