Swears in time about to get cross (8)
I believe the answer is:
traverse
'cross' is the definition.
('traverse' can be a synonym of 'cross')
'swears in time about' is the wordplay.
'swears' becomes 'avers' ('aver' can be a synonym of 'swear').
'in' is an insertion indicator.
'time' becomes 't'.
'about' becomes 're' (regarding**).
't'+'re'='tre'
'avers' inserted within 'tre' is 'TRAVERSE'.
'to get' acts as a link.
(Other definitions for traverse that I've seen before include "Cross sideways" , "Travel across or pass over" , "Ski diagonally across (a slope)" , "In mountaineering, a steep slope to be crossed from side to side" , "Move across" .)