Glasses chip at the bottom in short amounts of time (5)
'glasses' is the definition.
'chip at the bottom in short amounts of time' is the wordplay.
'at the bottom' suggests the final letters.
'in' is an insertion indicator.
'short amounts of time' becomes 'secs' (short for seconds).
The final letter of 'chip' is 'p'.
'p' put within 'secs' is 'SPECS'.
(Other definitions for specs that I've seen before include "Instructions", "provider of focus", "Glasses (informal)", "Glasses (sl.)", "shades?".)