Means of communication with a walrus (5)
I believe the answer is:
morse
This could be a double definition.
'means of communication' is the first definition.
'morse' can be an answer for 'communication' (morse is a kind of communication). I am not certain of the 'means of' bit.
'walrus' is the second definition.
(I've seen this before)
'with a' acts as a link.
Can you help me to learn more?
(Other definitions for morse that I've seen before include "Fictional inspector; code" , "Code; TV detective" , "Walrus - TV detective" , "Endeavour" , "used to transmit messages" .)