Good boys protecting kid in best clothes (4,4)
I believe the answer is:
glad rags
'best clothes' is the definition.
(I've seen this before)
'good boys protecting kid' is the wordplay.
'good' becomes 'g' (abbreviation).
'boys' becomes 'lads' (lad is a kind of boy).
'protecting' means one lot of letters goes inside another (inserted letters are held or protected).
'kid' becomes 'rag' (I've seen this in other clues).
'lads' placed around 'rag' is 'ladrags'.
'g'+'ladrags'='GLAD RAGS'
'in' is the link.
(Other definitions for glad rags that I've seen before include "Dressy clothes - happy threads" , "Fancy clothes for laggards" , "Best bib and tucker" , "What partygoers showed up in" , "Special kit" .)