What dons fired up when given new pad? (8)

'given new pad?' is the definition.
The definition and answer can be both to do with social activities as well as being past participle verbs.
Maybe they are linked in a way I don't understand?

'what dons fired up' is the wordplay.
'what' becomes 'eh' (sound used to ask 'what?' or 'pardon?').
'dons' means one lot of letters goes inside another (don means to wear or put on).
'fired up' becomes 'roused' (I am not sure about this - if you are sure you should believe this answer much more).
'eh' inserted into 'roused' is 'REHOUSED'.

'when' is the link.

Can you help me to learn more?