The doctor, for example, first seeks a deposit (5)
I believe the answer is:
dregs
'a deposit' is the definition.
(I know that dregs is a type of deposit)
'the doctor for example first seeks' is the wordplay.
'the doctor' becomes 'dr' (abbreviation).
'for example' becomes 'e.g.' (short for 'exempli gratia', 'for example' in Latin).
'first seeks' becomes 's' (1st letter of 'seeks').
'dr'+'eg'+'s'='DREGS'
(Other definitions for dregs that I've seen before include "Most worthless part (of anything)" , "Fluid remnants" , "Residue, lees" , "Wine or coffee residue" , "Bottom of the barrel" .)