Being late regularly, unless entering time machine (9)
I believe the answer is:
tardiness
'being late' is the definition.
(I've seen this before)
'regularly unless entering time machine' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'entering' is an insertion indicator.
'time machine' becomes 'tardis' (I've seen this before).
The alternating letters of 'unless' are 'nes'.
'nes' placed into 'tardis' is 'TARDINESS'.
(Other definitions for tardiness that I've seen before include "No quality in fast food" , "Being behind quality" , "being a little late" , "Unpunctuality" , "Becoming late" .)