Tsar who had to look out for trouble starting (5)
I believe the answer is:
peter
'tsar who had to look' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'out for trouble starting' is the wordplay.
'out' indicates putting letters inside.
'for' becomes 'peer' (I can't explain this - if you can you should give a lot more credence to this answer).
'starting' indicates taking the first letters.
The initial letter of 'trouble' is 't'.
'peer' going around 't' is 'PETER'.
Can you help me to learn more?
(Other definitions for peter that I've seen before include "In whist, play" , "and 14 dn Latest actor to play Doctor Who" , "Blue -, ship's flag" , "Saint's name" , "Apostle - saint - first Pope?" .)