Yielding person's first subject (7)
I believe the answer is:
pliable
'yielding' is the definition.
(I've seen this in another clue)
'person's first subject' is the wordplay.
'person's first' becomes 'p' (1st letter of 'person').
'subject' becomes 'liable'.
'p'+'liable'='PLIABLE'
(Other definitions for pliable that I've seen before include "accommodating" , "easily influenced" , "Flexible" , "Ductile" , "Easily bent" .)