Pig went for coarse plant (7)
I believe the answer is:
hogweed
'coarse plant' is the definition.
(hogweeds are coarse plants)
'pig went' is the wordplay.
'pig' becomes 'hog' (synonyms).
'went' becomes 'weed' ('go' can mean to urinate).
'hog'+'weed'='HOGWEED'
'for' acts as a link.
(Other definitions for hogweed that I've seen before include "Tall wild plant having thick stems and cluster of white to purple flowers" , "Large white-flowered plant" .)