Greek character placing ring on yours truly - much obliged! (4)
I believe the answer is:
iota
'greek character' is the definition.
(letter from the Greek alphabet)
I don't understand how the remainder of the clue works.
(Other definitions for iota that I've seen before include "Scintilla" , "Tiny or scarcely detectable amount" , "Just a jot, like Greek letter" , "Foreign character" , "Gr. letter; small amount" .)