Have branched off develop for two features
Feature A is nearly finished in terms of development but is on hold for a bit while the product owner does some research.
Developer started featureB but needs a small amount of core code from feature A.
What is the best practice in this case? I cannot assume that featureA and B would be in the same release.
Cheers
A very similar (yet not exactly the same) problem - including my answer - can be found in another SO post.
Regarding your problem your should use cherry-pick since you do not want to use all of featureA yet.