1.
If you ~ something unknown or uncertain, you find out exactly what it is.
It would be useful if you could ~ the source of this tension.
= pin down
PHRASAL VERB: V P n (not pron), also V n P
2.
If you ~ an agreement, you manage to reach a firm agreement with a definite result.
The Secretary of State and his Russian counterpart met to try to ~ the elusive accord.
PHRASAL VERB: V P n (not pron), also V n P