Amorous Cockney lead having a brief moment (6)
I believe the answer is:
erotic
'amorous' is the definition.
(I've seen this before)
'cockney lead having a brief moment' is the wordplay.
'cockney lead' becomes ''ero' ('hero' - I've seen this in other clues - said with the 'H' dropped - a cockney accent.).
'having' says to put letters next to each other.
'a brief' means to remove the last letter (a shorter or briefer version of the word).
'moment' becomes 'tick' (both can mean a very short amount of time).
'tick' with its last letter removed is 'tic'.
'ero'+'tic'='EROTIC'
(Other definitions for erotic that I've seen before include "Relating to sexual desire" , "Calculated to arouse sexual thoughts" , "Calculated to arouse sexual feelings" , "Conducive to arousing sexual desire" , "Amorous" .)