Denny piled ten awkwardly, without assistance (13)
I believe the answer is:
independently
'without assistance' is the definition.
(without depending on others)
'denny piled ten awkwardly' is the wordplay.
'awkwardly' indicates anagramming the letters.
'denny'+'piled'+'ten'='dennypiledten'
'dennypiledten' anagrammed gives 'INDEPENDENTLY'.
(Other definitions for independently that I've seen before include "Alone and unaided" , "without the help of others" .)