Second-rate student with awful big shoes to fill is on thin ice? (10)

'second-rate student with awful big shoes to fill is on thin ice?' is the definition.
I can't judge whether this definition defines the answer.

'second-rate student with awful big shoes to fill is' is the wordplay.
I cannot really understand how this works, but
'second' could be 's' (common abbreviation) and 's' is found in the answer.
'student' could be 'l' (as in L-plates for learner drivers) and 'l' is found within the answer.
'is' could be 'be' and 'be' is found in the remaining letters.
This explanation may well be incorrect...

Can you help me to learn more?