Stationary herds work the land (5-5)
I believe the answer is:
stock-still
'stationary' is the definition.
(thesaurus)
'herds work the land' is the wordplay.
'herds' becomes 'stocks' (I can't justify this - if you can you should give a lot more credence to this answer).
'work the land' becomes 'till' (I've seen this before).
'stocks'+'till'='STOCK-STILL'
Can you help me to learn more?
(Other definitions for stock-still that I've seen before include "Absolutely motionless" , "Completely motionless" , "Without any movement" .)