Noble band, all of similar age (4,5)
I believe the answer is:
peer group
'all of similar age' is the definition.
I can't tell whether this definition defines the answer.
'noble band' is the wordplay.
'noble' becomes 'peer' (peers are members of the nobility).
'band' becomes 'group' (I've seen this before).
'peer'+'group'='PEER GROUP'
Can you help me to learn more?
(Other definitions for peer group that I've seen before include "A segment of society who are associated and of equal status" , "set to meet in the upper house?" , "Those of equal age and ability, often influential" , "People who are associated with and of equal status" , "People like oneself" .)