Humbly asking for a favour (3,2,4)
I believe the answer is:
cap in hand
(Other definitions for cap in hand that I've seen before include "Go bareheaded thus to be obsequious" , "In begging posture" , "in a respectful way" , "with humility" , "Go . . . . . . . . . to beg humbly, clutching headgear?" .)