Female pig (3)
(Other definitions for goo that I've seen before include "Sticky stuff or sickly sentiment" , "Sentimentality (sl.)" , "syrup" , "Substance that's viscous" , "Slime" .)
'female pig' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sow that I've seen before include "She lives in 11" , "swine" , "Plant seeds for the pig" , "farm animal" , "Prepare farmland" .)