I offer footnote abbreviation (4)
I believe the answer is:
ibid
'footnote abbreviation' is the definition.
(I've seen this in another clue)
'i offer' is the wordplay.
'offer' becomes 'bid' (bid is a kind of offer).
'i'+'bid'='IBID'
(Other definitions for ibid that I've seen before include "(When citing a reference) in the same place (abbr)" , "Briefly, in the same book or passage" , "(With written references) in the same place (Latin)" , "In brief, notation meaning in came book or passage" , "(When citing a reference) in the same place (Latin)" .)