The odd couple start to make hay, just the stalk (4)
I believe the answer is:
culm
'stalk' is the definition.
(culm is a kind of stalk)
'the odd couple start to make' is the wordplay.
'the odd' indicates alternate letters.
'start to' indicates taking the first letters.
The initial letter of 'make' is 'm'.
The alternate letters of 'couple' are 'cul'.
'cul'+'m'='CULM'
'hay just the' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for culm that I've seen before include "coal dust" , "Coal-dust" .)