Thus wife becomes bearer of many young (3)
I believe the answer is:
sow
'bearer of many young' is the definition.
(a sow is a female pig)
'thus wife' is the wordplay.
'thus' becomes 'so' (synonyms).
'wife' becomes 'w' (abbreviation).
'so'+'w'='SOW'
'becomes' is the link.
(Other definitions for sow that I've seen before include "Plant seeds for the pig" , "Broadcast" , "swine" , "Prepare farmland" , "Plant seed in soil" .)