A secondary or subsidiary object, course, or undertaking; a side issue; something of minor importance: chiefly contrasted with main; whence phr. to…

An object lying aside from the main one; a subordinate end or aim; esp. a secret selfish purpose, a covert purpose of private advantage.

figurative. A lesser (esp. more achievable) goal which is subsidiary to or forms a step towards the main objective (cf. target, n.1 3f).