Itchy Y-fronts lacking an opening Y-shape (5)
I believe the answer is:
antsy
'itchy' is the definition.
(I've seen this in another clue)
'an opening y-shape' is the wordplay.
'opening' is a charade indicator (letters next to each other) (some letters appear before or \'open\' others).
'shape' becomes 'ts' (I can't justify this - if you can you should believe this answer much more).
'y' after 'ts' is 'tsy'.
'an'+'tsy'='ANTSY'
'y-fronts lacking' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for antsy that I've seen before include "excited?" , "Eager" , "nervous" .)