Drunkard reaches the summit with hesitation (5)
I believe the answer is:
toper
'drunkard' is the definition.
(I've seen this in another clue)
'the summit with hesitation' is the wordplay.
'the summit' becomes 'top' ('top' can be a synonym of 'summit').
'with' means one lot of letters go next to another.
'hesitation' becomes 'er' (sound made while hesitating - um, er).
'top'+'er'='TOPER'
'reaches' is the link.
(Other definitions for toper that I've seen before include "boozer" , "Regular drinker" , "Drinker, imbiber" , "Wino" , "Lush" .)