There are moments in a life that define a man. This was Mr Deane's. He was sprung for action and yet perfectly capable of blowing it completely.
My understanding of the line is that Mr. Deane stayed ready for action. However, I can't really get that from dictionary definitions of the verb "spring". Having plowed through the most exhaustive of dictionaries--the Oxford English Dictionary (OED), Wiktionary, Merriam-Webster-- I am still not sure if this usage has been defined and if there is a corresponding dictionary entry at all. And yes, I have checked Cambridge, Lexico (revamped ODO), Collins, and a few others. I thought to cause a mechanism to work, as in spring a trap might be close, but still sounds off the mark. This usage also seems analogous to a wind-up toy ready for action.
Here are some other examples:
Scalia is described as “perpetually sprung for action” during oral arguments, rocking in his chair “like a restless kid waiting for his turn at the blackboard.” (source)
Her right hand holds a cross-bow, sprung for action and armed with an arrow, pointing to the ground. (source)
...chart-table, which was designed to be collapsible, and in rough weather invariably did just that, was an open, man-sized hole from which a ten-rung ladder led down to the mess deck: he described it as 'a vicious mantrap sprung for action'. (source)
My question is: What exactly does "spring" mean in "spring for action"? Please point to a dictionary instead of pulling something out of a hat.