Dealing with a seaman, providing internal support (7)
I believe the answer is:
apropos
'providing internal support' is the definition.
I can't judge whether this defines the answer.
'dealing with a seaman' is the wordplay.
'dealing' becomes 'prop' (I can't explain this - if you can you should believe this answer much more).
'with' means one lot of letters go next to another.
'seaman' becomes 'OS' (short for ordinary seaman).
'prop' put after 'a' is 'aprop'.
'aprop'+'os'='APROPOS'
Can you help me to learn more?
(Other definitions for apropos that I've seen before include "With regard to" , "Touching" , "Appropriate" , "Incidentally - pertinent" , "well-chosen" .)