Peak figure attending hospital (6)
I believe the answer is:
height
'peak' is the definition.
('height' can be a synonym of 'peak')
'figure attending hospital' is the wordplay.
'figure' becomes 'eight' (I've seen this in other clues).
'attending' means one lot of letters go next to another.
'hospital' becomes 'h'.
'eight' after 'h' is 'HEIGHT'.
(Other definitions for height that I've seen before include "part of a patient's statistics?" , "summit" , "Measure it from top to bottom" , "Loftiness" , "Rising ground; extreme example" .)