Noticed polar opposites among children (6)
I believe the answer is:
sensed
'noticed' is the definition.
'polar opposites among children' is the wordplay.
'polar opposites' becomes 'ns' (I can't explain this - if you can you should believe this answer much more).
'among' means one lot of letters goes inside another (inserted letters are placed among others).
'children' becomes 'seed' (seed can mean one's offspring).
'ns' going within 'seed' is 'SENSED'.
Can you help me to learn more?
(Other definitions for sensed that I've seen before include "'Felt, perceived (6)'" , "Felt, tasted, etc" , "Became aware through mental perception or intuition" , "Became vaguely aware of (something)" , "Felt, had mental impression" .)