Gifted runner starts to long for undemanding legwork (7)
I believe the answer is:
skilful
'gifted' is the definition.
(thesaurus)
'runner starts to long for undemanding legwork' is the wordplay.
'runner' becomes 'ski' (ski is a kind of runner**).
'starts to' suggests taking the first letters.
The first letters of 'long for undemanding legwork' is 'lful'.
'ski'+'lful'='SKILFUL'
(Other definitions for skilful that I've seen before include "Deft" , "with expertise" , "7 [CLEVER]" , "Capable" , "exhibiting crafts" .)