Newborn child? No, a teen, strangely (7)
I believe the answer is:
neonate
'newborn child?' is the definition.
(I've seen this before)
'no a teen strangely' is the wordplay.
'strangely' indicates an anagram.
'no'+'a'+'teen'='noateen'
'noateen' with letters rearranged gives 'NEONATE'.
(Other definitions for neonate that I've seen before include "recently delivered" , "New-born child" , "Newborn baby" , "New baby" , "Young baby" .)