Expert runner was first to embrace learner (7)
I believe the answer is:
skilled
'expert' is the definition.
('skilled' can be similar in meaning to 'expert')
'runner was first to embrace learner' is the wordplay.
'runner' becomes 'ski' (ski is a kind of runner).
'was first' becomes 'led'.
'to embrace' is an insertion indicator.
'learner' becomes 'l'.
'led' going around 'l' is 'lled'.
'ski'+'lled'='SKILLED'
(Other definitions for skilled that I've seen before include "Trained, qualified" , "Showing great aptitude" , "Highly trained" , "Adept, clever" , "Competent - experienced" .)