Slow and careful French composer reduced tempo (10)
I believe the answer is:
deliberate
'slow' is the definition.
(thesaurus)
'french composer reduced tempo' is the wordplay.
'french composer' becomes 'Delibes' (Lo Delibes, 1836-1891).
'reduced' means to remove the last letter.
'tempo' becomes 'rate' (I've seen this in another clue).
'delibes' with its last letter taken away is 'delibe'.
'delibe'+'rate'='DELIBERATE'
'and careful' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for deliberate that I've seen before include "Done consciously" , "muse" , "Intentional; think carefully" , "Carefully thought out" , "Consider - intentional" .)