Very tiny (6)
(Other definitions for teensy that I've seen before include "Minute" , "Mini" , "Tiny" , "- - -weensy" , "Very small" .)
(Other definitions for micro that I've seen before include "Very little" , "Small computer" , "Prefix meaning tiny, or one-millionth of a unit" , "Prefix meaning very small or one millionth" , "minute" .)
'very tiny' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for wee that I've seen before include "squeal" , "Slash" , "number one" , "Little or tiny in Scotland" , "Minute" .)