Kind of cross summer’s a dry one (11)
I believe the answer is:
teetotaller
'a dry one' is the definition.
('dry' can mean avoiding alcohol)
'kind of cross summer's' is the wordplay.
'kind of cross' becomes 'tee' (a T-shaped cross).
'summer' becomes 'totaller' (someone summing or totalling things up).
'tee'+'totaller'='TEETOTALLER'
(Other definitions for teetotaller that I've seen before include "no supper!" , "One dry" , "Abstainer from drink" , "as observant Muslim, say" , "Non-drinker" .)