The rank of one forming an attachment? (4)
I believe the answer is:
tier
'the rank' is the definition.
(tier is a kind of rank)
'one forming an attachment?' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
The remaining letters 'ter' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for tier that I've seen before include "I might draw" , "Row, level" , "Wedding cake layer" , "Row (of seats)" , "Row - one forming a knot" .)