Technical details (4)
'technical details' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for specs that I've seen before include "Glasses (abbrev.)" , "shades?" , "Detailed plan" , "Instructions" , "Details for designer" .)
(Other definitions for spec that I've seen before include "Detailed design document (abbr.)" , "Description of requirements" , "Required standard of workmanship" , "Estimate" , "Risky investment" .)