Why to have information backed up off-line (5)
I believe the answer is:
wonky
'off-line' is the definition.
(not being aligned or in a line)
'why to have information backed up' is the wordplay.
'why' becomes 'y'.
'to have information' becomes 'know' (I've seen this before).
'backed up' is a reversal indicator.
'y'+'know'='yknow'
'yknow' in reverse letter order is 'WONKY'.
(Other definitions for wonky that I've seen before include "Faulty, unsound" , "Crooked, askew" , "A bit unstable" , "Not straight" .)