Sacks, say, country sides on way south (5)
I believe the answer is:
cysts
'sacks' is the definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.
'country sides on way south' is the wordplay.
'sides' means to remove the middle letters (only the letters on the sides are used).
'on' says to put letters next to each other.
'way' becomes 'st' (abbreviation for street).
'south' becomes 'S' (synonyms).
'country' with its middle removed is 'cy'.
'cy'+'st'+'s'='CYSTS'
'say' acts as a link.
Can you help me to learn more?
(Other definitions for cysts that I've seen before include "Body bags" , "Growths" , "Blister-like sacs" , "Body sacs" , "Sacs containing diseased matter" .)