Small hole I mentioned having obstruction (6)
I believe the answer is:
eyelet
'small hole' is the definition.
(I've seen this before)
'i mentioned having obstruction' is the wordplay.
'mentioned' indicates a 'sounds like' (homophone) clue.
'having' is a charade indicator (letters next to each other).
'obstruction' becomes 'let' (I've seen this in other clues).
'i' sounds like 'eye'.
'eye'+'let'='EYELET'
(Other definitions for eyelet that I've seen before include "peephole" , "Shoe hole for lacing" , "Small reinforced hole" , "Loophole" , "Small lace-hole in shoe (6)" .)