Dreamed of cool siesta at sea on date (10)
I believe the answer is:
fantasised
'dreamed' is the definition.
Both the answer and definition are past participle verbs.
Perhaps they are linked in a way I don't understand?
'cool siesta at sea on date' is the wordplay.
'cool' becomes 'fan' (fan can mean to cool down).
'at sea' indicates an anagram.
'on' is an insertion indicator (as in clothing 'on' a person).
'date' becomes 'd' (abbreviation e.g. dob - date of birth).
'siesta' anagrammed gives 'tasise'.
'fan' inserted within 'tasise' is 'fantasise'.
'fantasise'+'d'='FANTASISED'
'of' acts as a link.
Can you help me to learn more?
(Another definition for fantasised that I've seen is " imagined better circumstances".)