Crucial point about children in pack (5)
I believe the answer is:
bunch
'pack' is the definition.
(thesaurus)
'crucial point about children' is the wordplay.
'crucial point' becomes 'nub'.
'about' is a reversal indicator.
'children' becomes 'ch' (genealogical abbreviation).
'nub' back-to-front is 'bun'.
'bun'+'ch'='BUNCH'
'in' is the link.
(Other definitions for bunch that I've seen before include "Posy (of picked flowers)" , "Show silly fondness" , "Small group of flowers or people" , "Group (of bananas)" , "Gang" .)