Frank, with a gun, is so welcoming (4-5)
I believe the answer is:
open-armed
'so welcoming' is the definition.
'open-armed' can be an answer for 'welcoming' (I've seen this before). I am not certain of the 'so' bit.
'frank with a gun' is the wordplay.
'frank' becomes 'open' (synonyms).
'with' says to put letters next to each other.
'a gun' becomes 'armed' (I can't justify this - if you can you should give a lot more credence to this answer).
'open'+'armed'='OPEN-ARMED'
'is' acts as a link.
Can you help me to learn more?
(Another definition for open-armed that I've seen is " Welcoming".)