Indian queen moving ahead north to shower... (4)
I believe the answer is:
rain
'shower' is the definition.
(synonyms)
'indian queen moving ahead north' is the wordplay.
I cannot quite see how this works, but
'queen' could be 'r' (r is abbreviation regina. e.g. in ER ) and 'r' is located in the answer.
'north' could be 'n' (synonyms) and 'n' is found within the answer.
The remaining letters 'ai' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'to' is the link.
(Other definitions for rain that I've seen before include "Falling moisture" , "Fall wetly" , "See 12" , "Wet weather" , "previous rule?" .)