A lot of snow, so unable to steer (6)
I believe the answer is:
adrift
'unable to steer' is the definition.
I can't tell whether this definition defines the answer.
'a lot of snow' is the wordplay.
'lot' becomes 'd'.
'of snow' becomes 'rift' (I can't explain this - if you can you should give a lot more credence to this answer).
'a'+'d'+'rift'='ADRIFT'
'so' acts as a link.
Can you help me to learn more?
(Other definitions for adrift that I've seen before include "cut loose" , "Rudderless, astray" , "Floating freely, not moored" , "Wandering aimlessly" , "like Mary Celeste?" .)