Nine teens worried about another number (7)
I believe the answer is:
sixteen
'another number' is the definition.
'sixteen' can be an answer for 'number' (sixteen is a kind of whole number). I am unsure of the 'another' bit.
'nine teens worried about' is the wordplay.
'nine' becomes 'IX' (roman numeral).
'worried' indicates anagramming the letters (worry can mean to interfere with or disturb).
'about' is an insertion indicator.
'teens' anagrammed gives 'steen'.
'ix' going into 'steen' is 'SIXTEEN'.
Can you help me to learn more?
(Other definitions for sixteen that I've seen before include "XVI" , ""Sweet" age?" , "4 x 4" , "Year for which 6 is remembered historically" , "8 x 2" .)