Three lines husband put on road margins finally to park Daihatsu (5)
I believe the answer is:
'three lines' is the definition.
(I've seen this before)
'husband put on road margins finally to park daihatsu' is the wordplay.
'husband' becomes 'h'.
'put on road margins' becomes 'ai' (I can't explain this - if you can you should give a lot more credence to this answer).
'finally' says to take the final letters.
The last letters of 'park daihatsu' are 'ku'.
Can you help me to learn more?
(Other definitions for haiku that I've seen before include "Japanese three-line poem of 17 syllables", "Japanese 3-line poem of 17 syllables", "Epigrammatic verse", "Type of Japanese poem", "ode".)