Wet jacket of wholesome girl coming out climbing (5)
I believe the answer is:
bedew
'wet' is the definition.
(bedewing is a kind of wetting)
'jacket of wholesome girl coming out climbing' is the wordplay.
'jacket of' suggests removing the centre (only the word's outer letters or 'jacket' remain).
'girl coming out' becomes 'deb' (abbreviation for debutante).
'climbing' shows that the letters should be reversed in order (in a down clue, letters climb up).
'wholesome' with its middle taken out is 'we'.
'we'+'deb'='wedeb'
'wedeb' backwards is 'BEDEW'.
(Other definitions for bedew that I've seen before include "Sprinkle with water (poetic)" , "Moisten (poetic)" .)