Walk unsteadily in summer? (6)
I believe the answer is:
totter
I believe this is a double definition.
'walk unsteadily' is the first definition.
(I've seen this before)
'summer?' is the second definition.
(someone who does sums or tots things up)
'in' is the link.
(Other definitions for totter that I've seen before include "Lurch" , "Proceed unsteadily" , "Be unsteady on one's feet" , "Rag-and-bone man - summer" , "Maybe a mathematician" .)