Male gymnast's head breaks weak beam (5)
I believe the answer is:
gleam
'weak beam' is the definition.
'gleam' can be an answer for 'beam' (thesaurus). I am not certain of the 'weak' bit.
'male gymnast's head breaks' is the wordplay.
'head' says to take the initial letters.
'breaks' indicates an anagram.
The first letter of 'gymnasts' is 'g'.
'male'+'g'='maleg'
'maleg' is an anagram of 'GLEAM'.
Can you help me to learn more?
(Other definitions for gleam that I've seen before include "Coruscate" , "Brief bright light" , "Glint" , "Brightness" , "Small stream of light" .)