Is able to admit Irish ship is spick and span (5)
I believe the answer is:
clean
'spick and span' is the definition.
(I've seen this before)
'is able to admit irish ship' is the wordplay.
'is able to' becomes 'can' (if you can do something you are able to do it).
'admit' indicates putting letters inside.
'irish ship' becomes 'le' (I can't justify this - if you can you should believe this answer much more).
'can' going around 'le' is 'CLEAN'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for clean that I've seen before include "Squeaky?" , "Not prohibited" , "Pure, hygienic" , "How confessor comes" , "Free from contamination - entirely" .)