Everyman 3699 - All Done But Can't Parse One

[Beverley]

25a Much occupying one when about to make expedition (6)

I am sure the answer is SAFARI but would like help to parse it please.

Thanks

[Mamyalynne]

When -as - about - Sa
Much - Far
One - i

[Lie-in King]

Safari - 'far' (much, in) 'i (one) as (when)' (about; back)

[dannyk13]

as (when ) reversed + far(much) +i(one)

[Celticv11]

When= as about =sa + much =far + one=I?

[Beverley]

Thank you all.