Impressive summer period (6)
I believe the answer is:
august
I believe this is a triple definition!
'impressive' is the first definition.
(I've seen this before)
'summer' is the second definition.
(I've seen this before)
'period' is the third definition.
(August is an example)
(Other definitions for august that I've seen before include "part of the summer" , "Impressive, majestic" , "a period for taking holidays?" , "Eighth month" , "A grand month?" .)