Give up in seconds, boxed by English champ (6)
I believe the answer is:
eschew
'give up' is the definition.
(I've seen this before)
'seconds boxed by english champ' is the wordplay.
'seconds' becomes 's' (abbreviation).
'boxed by' means one lot of letters goes inside another (I've seen this in other clues).
'english' becomes 'E' (abbreviation).
'champ' becomes 'chew' (I've seen this before).
'e'+'chew'='echew'
's' put into 'echew' is 'ESCHEW'.
'in' acts as a link.
(Other definitions for eschew that I've seen before include "Deliberately avoid" , "Don't use" , "Abstain from (an activity)" , "Avoid or abstain from (6)" , "Deliberately stay away from" .)