He composes a letter to suit (5)
I believe the answer is:
Here is my best explanation:
'he' is the definition.
'composes a letter to suit' is the wordplay.
I cannot really see how this works, but
'letter' could be 'u' and 'u' is present in the answer.
The remaining letters 'tits' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
(Other definitions for titus that I've seen before include "Only part of Shakespeare play", "recipient of holy letter", "saint", "Roman emperor, son of Vespasian", "Groan, say", "Groan maybe", "Emperor, son of Vespasian", "good book", "NT book" and "A Roman emperor; a Pauline addressee".)