Back in two hours, perhaps to redesign them - they're a bit old-fashioned (10)
I believe the answer is:
throwbacks
'to redesign them they're a bit old-fashioned' is the definition.
The definition suggests an adverb but the answer is not.
'back in two hours' is the wordplay.
'in' indicates putting letters inside.
'two hours' becomes 'throws' (I can't explain this - if you can you should give a lot more credence to this answer).
'back' placed inside 'throws' is 'THROWBACKS'.
'perhaps' acts as a link.
Can you help me to learn more?
(Another definition for throwbacks that I've seen is " retrograde types".)