Look happy if occasionally finding forest giraffe (5)
I believe the answer is:
okapi
'forest giraffe' is the definition.
'okapi' can be an answer for 'giraffe' (okapi is a kind of giraffe). I am unsure of the 'forest' bit.
'look happy if occasionally' is the wordplay.
'occasionally' means one should take alternating letters.
'look'+'happy'+'if'='lookhappyif'
The alternating letters of 'lookhappyif' are 'OKAPI'.
'finding' is the link.
Can you help me to learn more?
(Other definitions for okapi that I've seen before include "Beast related to giraffe" , "Hoofed mammal" , "African mammal related to giraffe" , "Giraffe-related mammal" , "Animal of central Africa" .)