Name-dropping family member in Northern Ireland's central parts (6)
I believe the answer is:
nuclei
'central parts' is the definition.
(plural of nucleus)
'name-dropping family member in northern ireland's' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'dropping' indicates named letters should be taken away (some letters drop out).
'family member' becomes 'uncle' (brother of a parent).
'in' means one lot of letters goes inside another.
'northern ireland' becomes 'NI' (abbreviation).
'uncle' with 'n' taken out is 'ucle'.
'ucle' put inside 'ni' is 'NUCLEI'.
(Other definitions for nuclei that I've seen before include "Central parts of atoms" , "Atomic cores" , "Cores of atoms" , "Atom cores" , "Central pieces" .)