Sour look on a day for transfer (7)
I believe the answer is:
offload
'for transfer' is the definition.
(to offload is to transfer to somewhere else)
'sour look on a day' is the wordplay.
'sour' becomes 'off' (synonyms).
'look' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'on' is a charade indicator (letters next to each other).
'day' becomes 'd' (abbreviation for day).
'off'+'lo'+'a'+'d'='OFFLOAD'
(Other definitions for offload that I've seen before include "Dump" , "Get rid of (unwanted item or burden)" , "9 [JETTISON]" , "deliver goods" .)