Encourage seafront exercises (6)
I believe the answer is:
prompt
'encourage' is the definition.
(I've seen this before)
'seafront exercises' is the wordplay.
'seafront' becomes 'prom' (short for promenade).
'exercises' becomes 'PT' (Physical Training).
'prom'+'pt'='PROMPT'
(Other definitions for prompt that I've seen before include "Bring about; actors' help" , "Incite - punctual" , "Speedy - help for forgetful actor" , "Cause, bring about" , "Cause; on time" .)