Wet weather during break time is a limitation (9)
I believe the answer is:
restraint
'a limitation' is the definition.
(I know that restraint is a type of limitation)
'wet weather during break time' is the wordplay.
'wet weather' becomes 'rain' (rain is wet weather).
'during' means one lot of letters goes inside another.
'break' becomes 'rest' (a rest is taking a break).
'time' becomes 't' (abbreviation).
'rest'+'t'='restt'
'rain' inserted within 'restt' is 'RESTRAINT'.
'is' acts as a link.
(Other definitions for restraint that I've seen before include "Moderation" , "Controlling measure" , "Restriction, limit" , "Start rain as an impediment" , "Self-control" .)