Lies flat in blind spot at first (4)
I believe the answer is:
fibs
'lies' is the definition.
(I know this)
'flat in blind spot at first' is the wordplay.
'at first' says to take the initial letters.
The first letters of 'flat in blind spot' is 'FIBS'.
(Other definitions for fibs that I've seen before include "Trivial lies as by child" , "Little white lies" , "Harmless little lies" .)