Ignore trade union by getting let off (4,1,5,3,2)
I believe the answer is:
turn a blind eye to
'ignore' is the definition.
(turning a blind eye to is a kind of ignoring)
'trade union by getting let off' is the wordplay.
'getting' is a charade indicator (letters next to each other).
'off' indicates anagramming the letters.
'trade'+'union'+'by'+'let'='tradeunionbylet'
'tradeunionbylet' with letters rearranged gives 'TURN A BLIND EYE TO'.
(Other definitions for turn a blind eye to that I've seen before include "Ignore" , "overlook" .)