Small part of what comes next said you fell in love head over heels (5)
I believe the answer is:
ovule
'small part' is the definition.
'ovule' can be an answer for 'part' (I have seen 'Part of flower' mean 'ovule' so perhaps 'part' could also mean 'ovule'). I am unsure of the 'small' bit.
'what comes next said you fell in love head over heels' is the wordplay.
I cannot really see how this works, but
'you' could be 'u' (I've seen this in other clues) and 'u' is found within the answer.
an anagram of 'love' is 'ovle' which is within the left over letters.
No letters remain.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for ovule that I've seen before include "Part of seed plants" , "Egg cell" , "Undeveloped seed" , "Small body containing the female germ cell of a plant" , "Part of plant ovary which becomes seed" .)