Great soul in Derby perhaps absorbed by mother (7)
I believe the answer is:
mahatma
'great soul' is the definition.
'derby perhaps absorbed by mother' is the wordplay.
'derby perhaps' becomes 'hat' (derby is a kind of hat).
'absorbed by' means one lot of letters goes inside another.
'mother' becomes 'mama' (mama is a kind of mother).
'hat' going inside 'mama' is 'MAHATMA'.
'in' is the link.
(Other definitions for mahatma that I've seen before include "Gandhi's title" , "Hindu leader" , "(Indian) holy person or sage" , "Sage (as e.g. Gandhi)" , "Gandhi, for example" .)