Poach trout to begin with, adding last of asparagus spears chopped up (8)
I believe the answer is:
trespass
'poach' is the definition.
(I've seen this in another clue)
'trout to begin with adding last of asparagus spears chopped up' is the wordplay.
'to begin with' says to take the initial letters.
'adding' means one lot of letters go next to another.
'last of' says to take the final letters.
'chopped up' indicates an anagram.
The initial letter of 'trout' is 't'.
The last letter of 'asparagus' is 's'.
's'+'spears'='sspears'
'sspears' anagrammed gives 'respass'.
't'+'respass'='TRESPASS'
(Other definitions for trespass that I've seen before include "Intrude on another's property" , "Enter land without permission" , "Intrude, encroach" , "Illegal entry" , "Go out of bounds" .)