One can work things out using this playground equipment control (5,4)
I believe the answer is:
slide rule
'one can work things out using this playground' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'equipment control' is the wordplay.
'equipment' becomes 'slide' (I can't justify this - if you can you should believe this answer much more).
'control' becomes 'rule' (synonyms).
'slide'+'rule'='SLIDE-RULE'
Can you help me to learn more?
(Other definitions for slide rule that I've seen before include "Old calculator" , "Old calculating device" , "facilitates calculations" , "Obsolete calculator" , "Instrument for rapid calculations" .)