A little hat most Americans have (3)
I believe the answer is:
tam
'a little hat' is the definition.
'tam' can be an answer for 'hat' (thesaurus). I'm unsure of the 'a little' bit.
'most americans have' is the wordplay.
'have' indicates the answer is hidden within the clue.
'TAM' is hidden in the letters of 'most americans'.
Can you help me to learn more?
(Other definitions for tam that I've seen before include "'Woollen cap of Scottish origin, in short (3)'" , "Scotsman's cap" , "These ratings measure TV audiences" , "TV audience ratings" , "Television ratings system" .)