We’ll go after you, I say, first night if under the weather (6)
I believe the answer is:
unwell
'under the weather' is the definition.
(I've seen this in another clue)
'we'll go after you i say first night' is the wordplay.
I cannot quite understand how this works, but
'we'll' could be 'well' and 'well' is located in the answer.
'you' could be 'u' (homophones) and 'u' is present in the answer.
'first night' could be 'n' (1st letter of 'night') and 'n' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'if' acts as a link.
Can you help me to learn more?
(Other definitions for unwell that I've seen before include "Poorly" , "Off-colour" , "Out of sorts" , "funny" , "Sick, not in good health" .)