It's spread as a piece of American symbolism (5)
I believe the answer is:
eagle
'piece of american symbolism' is the definition.
'eagle' can be an answer for 'piece' (I have seen 'Valuable piece' mean 'eagle' so perhaps 'piece' could also mean 'eagle'). I'm not certain of the 'of american symbolism' bit.
'it's spread as a' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'as' could be 'eg' ('as' and 'e.g.' can both mean for example) and 'eg' is found within the leftover letters.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found within the answer.
A single letter 'l' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for eagle that I've seen before include "King of birds" , "standard for the military is seen" , "Bird of prey; former children's comic" , "flier" , "Flyer" .)