Wet day touring site in need of development (7)
I believe the answer is:
moisten
'wet' is the definition.
(moistening is a kind of wetting)
'day touring site in need of development' is the wordplay.
'day' becomes 'mon' (abbreviation for Monday).
'touring' indicates putting letters inside (touring can mean going round).
'in need of development' indicates an anagram (letters developed in another way).
'site' is an anagram of 'iste'.
'mon' going around 'iste' is 'MOISTEN'.
(Other definitions for moisten that I've seen before include "contrary to sixteen down [DEHYDRATE]!" , "Add water - dampen" , "Make damp, say lips with tongue" , "What one's eyes may do!" , "Make damp or slightly wet" .)