Tackling debt lord is occasionally offensive (6)
I believe the answer is:
odious
'offensive' is the definition.
(I've seen this in another clue)
'tackling debt lord is occasionally' is the wordplay.
'tackling' means one lot of letters goes inside another (to tackle is to take possession of).
'debt' becomes 'iou' (I owe you, a promise to pay a debt).
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'lord'+'is'='lordis'
The alternate letters of 'lordis' are 'ods'.
'iou' placed into 'ods' is 'ODIOUS'.
(Other definitions for odious that I've seen before include "Detestable, greatly disliked" , "Loathsome and repulsive" , "Comparisons are said to be thus" , "Hateful, really nasty" , "Replusive, abhorrent (6)" .)