OP writes:
It would make more sense to me if the word [for] were left out
that is , left out of the definition to gain favor or favorable acceptance for by deliberate effort
.
The preposition for there means "on behalf of".
The dictionary definition you cited is elliptical. It is leaving something out. The dictionary has left out {something}
and it has left out {from someone}
.
We seek acceptance for {something} from {someone}.
For example, for a proposal, or an action we intend to take. That is, we seek to have that thing be accepted (by someone). We seek their acceptance of it.
We are proposing to turn the southwest corner of Elm Street and Main Street into a children's playground. We are seeking acceptance for this proposal. Will you sign our petition?
The definition is elliptical because these things it has left out, something
and from someone
, are "variables" or "slots" that will always be implicitly present on a semantic level, and the definition is focusing narrowly on the action per se.
If we seek acceptance, without the preposition for and without the object of for, that is, whatever the "something" happens to be, we are seeking acceptance on behalf of ourselves, not on behalf of something else, and what we want to be accepted is ourselves.
The wolf showed up in the territory of another pack and sought acceptance there.