Make clear you'll get back under your own steam (5,4)
I believe the answer is:
drive home
'own steam' is the definition.
Although both the answer and definition are verbs in their base form, I don't see how they can define each other.
'make clear you'll get back under your' is the wordplay.
I cannot really see how this works, but
'make' could be 'drive' (driving is a kind of making) and 'drive' is found within the answer.
'get back' could be 'home' (homing is a kind of getting back) and 'home' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for drive home that I've seen before include "Return journey" , "evening commute?" , "impress" , "What some commuters do after work" , "Force (a nail) completely in" .)