Ignore past and go (6)
I believe the answer is:
bypass
'ignore' is the definition.
(I've seen this before)
'past and go' is the wordplay.
'past' becomes 'by' (as in years gone by).
'and' means one lot of letters go next to another.
'go' becomes 'pass' (passing is a kind of going).
'by'+'pass'='BYPASS'
(Other definitions for bypass that I've seen before include "Ring road" , "Go round (congested area etc)" , "not found in the high street" , "Circuitous route (for traffic, fluids etc)" , "Round-about way" .)