Small, strange dash is wet (6)
I believe the answer is:
sodden
'is wet' is the definition.
(similar in meaning)
'small strange dash' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'strange' becomes 'odd' (I've seen this before).
'dash' becomes 'en' (an en dash is a dash as wide as a letter 'n').
's'+'odd'+'en'='SODDEN'
(Other definitions for sodden that I've seen before include "heavy with moisture" , "Waterlogged" , "Muddy" , "Drenched through, really wet" , "Completely saturated" .)