Beat, but less than instantly (3)
I believe the answer is:
tan
'beat' is the definition.
(tan can mean to beat or hit)
'less than instantly' is the wordplay.
'less' says the answer is hidden in the clue (the clue less some of the letters in it).
'TAN' is hidden within 'than instantly'.
'but' acts as a link.
(Other definitions for tan that I've seen before include "Catch the sun" , "Yellowish brown" , "Brown to beat" , "Shade of brown" , "Make hide into leather - nicely brown" .)