Little old man retired, lacking in desire (6)
I believe the answer is:
choice
'desire' is the definition.
(thesaurus)
'little old man retired lacking in' is the wordplay.
'little old' becomes 'o' (abbreviation for old).
'man' becomes 'chic' ().
'retired' becomes 'ex' (prefix meaning former or onetime).
'lacking' means to remove the last letter (the word is incomplete or lacking).
'in' means one lot of letters goes inside another.
'ex' with its last letter taken away is 'e'.
'chic'+'e'='chice'
'o' going into 'chice' is 'CHOICE'.
(Other definitions for choice that I've seen before include "Variety" , "Very good" , "'Selection, option (6)'" , "Plum" , "Volition" .)