Elaborate dress: set out before noon to gain impetus (3,2,5)

'gain impetus' is the definition.
(to get up steam is to build momentum)

'elaborate dress set out before noon' is the wordplay.
I cannot really understand how this works, but
'dress' could be 'getup' (getting up is a kind of dressing) and 'getup' is located in the answer.
an anagram of 'set' is 'ste' which is within the answer.
'noon' could be 'm' and 'm' is found in the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This explanation may well be incorrect...

'to' is the link.