Feel sorry for mine, and yours at first (4)
I believe the answer is:
pity
'feel sorry' is the definition.
(I've seen this before)
'mine and yours at first' is the wordplay.
'mine' becomes 'pit' (down the pit**).
'and' means one lot of letters go next to another.
'at first' says to take the initial letters.
The first letter of 'yours' is 'y'.
'pit'+'y'='PITY'
'for' is the link.
(Other definitions for pity that I've seen before include "Commiseration" , "Sorrow for the misfortunes of others" , "Matter for regret" , "Cause of disappointment" , "Sympathy and sorrow" .)