Strive to employ cockney to follow snake (6)
I believe the answer is:
aspire
'strive' is the definition.
(I've seen this in another clue)
'employ cockney to follow snake' is the wordplay.
'employ cockney' becomes ''ire' ('hire' - synonyms - said with the 'H' dropped - a cockney accent.).
'to follow' means one lot of letters go next to another (some letters go after or follow others).
'snake' becomes 'asp' (asp is a kind of snake).
'ire' after 'asp' is 'ASPIRE'.
'to' acts as a link.
(Other definitions for aspire that I've seen before include "Aim at, work towards" , "Yearn, dream (towards)" , "Have an ambitious plan or a lofty goal" , "Desire (to reach higher things)" , "rise to a great height" .)