He tangles with cop - that will mean time (5)
I believe the answer is:
epoch
'time' is the definition.
(epoch is a kind of time)
'he tangles with cop' is the wordplay.
'tangles with' is an anagram indicator (I've seen 'tangle' mean this).
'he' with its letters anagrammed with 'cop' makes 'EPOCH'.
'that will mean' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for epoch that I've seen before include "Particular historic time period" , "Period of time in history" , "Long period of time" , "Significant period" , "Distinctive period of time" .)