Exegesis:

epērōtōn ‘asked,’ imperfect tense, implying that the act of asking is incomplete in itself.

hoi mathētai autou ‘his disciples,’ i.e. the larger group of followers, cf. 6.13, 20.

tis hautē eiē hē parabolē ‘what this parable was,’ i.e. meant. hautē goes with hē parabolē (hyperbaton).

Translation:

What this parable meant, or, ‘what (was) the meaning/intent of this parable’; or in direct discourse, e.g. ‘What then (is) the meaning (lit. solution, as of a riddle) of this parable?’ (Tae’).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.