Sportsman's assistant taken in hand for instruction (7)
I believe the answer is:
pointer
'instruction' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'sportsman's assistant taken in hand' is the wordplay.
'sportsman's assistant' becomes 'pote' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'taken' is an insertion indicator.
'hand' becomes 'R' (abbreviation for right, as in the right-hand side).
'pote' enclosing 'in' is 'pointe'.
'pointe'+'r'='POINTER'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for pointer that I've seen before include "Tip; dog" , "Suggestion" , "Guide" , "under control of mouse" , "helpful tip!" .)