Seeing deer, occasionally, from peak first scaled by Wicklow man (5)
I believe the answer is:
eiger
'peak first scaled by wicklow man' is the definition.
The definition suggests a singular noun which matches the answer.
'seeing deer occasionally' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'seeing'+'deer'='seeingdeer'
The alternate letters of 'seeingdeer' are 'EIGER'.
'from' is the link.
Can you help me to learn more?
(Other definitions for eiger that I've seen before include "Mountains in Bernese Alps" , "Swiss mountain with a notorious north face" , "Famous Swiss mountain" , "Keen" , "Alpine mountain" .)