Beat poet cleverly controls metre (5)
I believe the answer is:
tempo
'beat' is the definition.
(I've seen this in another clue)
'poet cleverly controls metre' is the wordplay.
'cleverly' indicates anagramming the letters.
'controls' means one lot of letters goes inside another.
'metre' becomes 'm' (synonyms).
'poet' is an anagram of 'tepo'.
'tepo' enclosing 'm' is 'TEMPO'.
(Other definitions for tempo that I've seen before include "Cadence" , "Time (music)" , "Musical time" , "Rhythm, metre" , "Rate and rhythm in music" .)