Intends to put a large picture up outside (5)
I believe the answer is:
plans
'intends' is the definition.
(planning is a kind of intending)
'a large picture up outside' is the wordplay.
'a large' becomes 'L' (eg in clothes sizes).
'picture' becomes 'snap' (I've seen this before).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'outside' indicates putting letters inside (some letters go outside others).
'snap' back-to-front is 'pans'.
'l' inserted into 'pans' is 'PLANS'.
'to put' acts as a link.
(Other definitions for plans that I've seen before include "Designs" , "maps" , "Schemes; intentions" , "Detailed proposals for doing something" , "Schemes; diagrams" .)